In my eyes, the goal of this discussion is to eliminate what we deem to be uncompetitive and banworthy from various generations without compromising or ruining legitimate strategies.
For this to be done, I think a case by case approach (individual action for each generation that needs something done) is better than a blanket ban. A blanket ban is general, as various above posters stated, and will never be the best fit for every generation. For example, if we banned the move baton pass from every generation (which is an extreme that I'm not proposing, just using as an example), then all of these issues would be solved, but a plethora of viable strategies would be ruined at the same time. On the other side of the spectrum, if we implemented a ban akin to the generation six ban to each gen, dealing with multiple BP users per team, it would only cover some of the issues (the various forms of quick-pass you see in current ORAS OU and SmashPass in BW/ORAS would still remain unaffected). Given the above, I'll talk about what I believe to be the best specific solutions for each generation's baton pass problem, or lack thereof, but I'll stay within areas which I have sufficient knowledge (BW and ORAS).
I'll start with BW. As the OP states, BW has two forms of BP for the most part - Smash Pass and Full BP. Both of these are as effective as they are primarily because of Espeon gaining access to Magic Bounce, which gets in the way of most counterplay to BP that was present in previous generations. With this taken into consideration, I'll first give my input as to if I think they're banworthy or not and then state the best solution, in my opinion.
Smash Pass is potent and only needs a safe turn or two, which isn't hard to get given the fact that screens will usually be up, and then you've got a mixrach or a mixmence with +2/+2/+2 in while your opponent is likely lacking a way to stop this pokemon from sweeping. I am not for just picking an example up and saying "look how good it did, it must be broken", but if a strategy is consistently successful and the opponent doesn't stand much of a chance so often, then you have to draw a line at some point - going onto some examples of smash pass that I feel speak volumes about its success: Shake won a BW OU live tour using Smash Pass every round (I even got two crits vs him in finals, but still managed to lose to his mence in the long run although I could have played a bit differently had I known all of the sets while another competent BW player, Leftiez, wasn't able to do much vs SmashPass either, despite having a solid team and playing around the first Shell Smasher) and the game linked in the OP of Omfuga vs Shake for BW Cup, where Omfuga used a standard Moltres rain team I gave him (he even slapped Haze onto Scarf Politoed, but you'll see more about this later in my post), shows Smash Pass dominating a semi-standard team archetype. There are infinite examples thanks to various people using Smash Pass to great success in Smogon Tour, Classic, etc. and I think that a strategy that leaves so little room for counterplay and minimal room for error whatsoever when playing against is not a competitive strategy, nor one that is healthy for the metagame. Furthermore, I think that Smash Pass needs to be addressed in BW.
How should it be addressed? The most direct solution is a ban of Baton Pass + Shell Smash in the same moveset (which was stated as an option in the OP). Going back to the purpose of this thread that I listed at the start of my post, this ban would put an end to the strategy that is banworthy while not having any effects on other strategies. This sort of specific complex ban has provoked a lot of fuss over the years because it's unprecedented in some areas and the justification behind it is shaky, but if we can limit the number of users with baton pass on a given team (which we did in generation six), then I see no reason why we can't go further and restrict movesets that we deem broken (such as BP + SS) as it would be sort of an arbitrary stoppage point to limit potential bans to number of users on a team when moveset bans would provide a direct solution to this problem.
Full BP is a whole other can of worms. I'm going to jump right into showing how hard it is to deal with it by referring back to the Omfuga vs Shake series for BW Cup, except using a different game, where Shake uses full BP instead of Smash Pass while Omfuga uses the same team, but this time Haze Politoed gets a use, but Omfuga still stands no chance bar a few extra opportunities to land a well-timed crit. To beat full BP, odds are you're going to need to continuously apply offensive pressure to your opponent and either crit at the right time or out-sweep them early and quickly, before it's too late and Espeon is sweeping you with Stored Power as you say "fuck pokemon" and eventually rage quit on your opponent haha. Going back to the main topic, full BP with no limits on the amount of BP users has the ability to adapt to normal counterplay and win a devastatingly high proportion of tour games it's used in (Espeon, a staple on these teams, has a win percentage of 65% in BW2 OU Smogon tour games this season and I bet it's even higher than that when being used on full BP because the rare occurance of seeing Espeon on a sun team and Espeon is also on SmashPass, which has a less reliable/consistent win rate). Before you ask 'why not just get rid of Espeon', I was just using it as an example as it's on every full BP team and it's pretty symbolic of the full BP archetype; there are better bans that wouldn't compromise a pokemon that has (albeit minimal) other uses. Anyway, the point of this is that full Baton Pass is nearly unbeatable using a lot of bulkier/slower paced teams and even when you're using something with a win condition or two and lots of offensive pressure, you have to execute perfectly in a short period of time just to have a shot to break through BP (you may still need to catch a lucky break to beat it depending on circumstances). Allowing a strategy with this capability isn't something anyone should want, so I'd think that bp deserves to be addressed in BW.
How should it be addressed? The solution that eliminates the current state of BP while not compromising any current outstanding strategies would be limiting the amount of BP users, similar to what is done in generation six and what is proposed in the OP, but I'm not sure if it should be to one or two users or what - that's trivial at this point, what matters is that the amount of users should be limited and once that's established, then the specific amount can be discussed if it's up for question.
Now onto ORAS. I know that Smash Pass is a thing in ORAS (that team with Whimsicott, Mega Diancie, Azelf, Gorebyss, Lucario, and Lando (before it was banned, idk what replaces it now)) and I've seen it in use before, but I honestly haven't played against it once (thankfully) and haven't seen it too many times to feel comfortable commenting, although the replays in the OP seem to be pretty indicative of how it is as a strategy. Regardless, to be fair and not risk misrepresenting ORAS SmashPass, I'll refrain from commenting on it for now. However, I will leave my thoughts on this GeoPass that was created, popularized, and abused to death after the baton pass limit was implemented. Essentially, it sets up screens, gets a memento off, usually gets a tailwind off, and then passed a Geomancy to an Espeon which is essentially invincible unless you have one of a very select few things or you manage to sweep the GeoPass team before it gets these conditions and the Geomancy up. The systematic and consistent success of this style just attests to the overall problematic nature of Baton Pass variants dating back to BW and still lasting today. It's actually a bit harder to argue for this GeoPass to be considered broken, when looking at it in perspective, as it does require a lot of support in the screens, memento, and tailwind, but they all are set up in order and the pokemon are essentually suicide mons to lead up to the sweep, so it's not really physical support, more like any other team member that synergizes well with a win condition, I suppose. Regardless, this archetype, like BW smash pass, will get the job done against passive teams that cannot get in the way of the supporters and eventual GeoPass to Espeon while still doing well against offense as memento and screens interfere with their immediate attempts to sweep and if the game gets prolonged, offense will eventually lose to espeon with a geomancy unless there is one of the few ways to prevent Smeargle from setting up despite having sash, screens, memento momentum, etc. I'd also like to point out the Smogon Tour usage stats again - Smeargle has a 71% win rate and Espeon has a 60% win rate (probably higher on GeoPass as Smeargle's restricted to this archetype as far as I know and it sits 11% higher, but can't say for sure). Smeargle's rate is absurdly high for a 'gimmick' pokemon that only has viability on one archetype, so it's fair to say that this variant of BP should go given this piece of evidence and the systematic nature of it that I mentioned before (Screens+TWind+Memento leads to Geo+Pass leads to death).
How should it be addressed? Banning the move Geomancy is the best way to go as nothing in OU uses Geomancy, it's the root of the problem given that it is being passed, and there was another move ban this generation, there's at least a slight precedent for it (although Geomancy and Swagger aren't really comparable, there's at least some justification and this is another solution that eliminates the problem without compromising any viable strategies, which I'm trying to emphasize here).
Overall, I generally agree with the OP's proposals for dealing with these issues and given my analysis of the various styles I discussed, I'm leaning to the side that these specific variants of BP are banworthy.
For this to be done, I think a case by case approach (individual action for each generation that needs something done) is better than a blanket ban. A blanket ban is general, as various above posters stated, and will never be the best fit for every generation. For example, if we banned the move baton pass from every generation (which is an extreme that I'm not proposing, just using as an example), then all of these issues would be solved, but a plethora of viable strategies would be ruined at the same time. On the other side of the spectrum, if we implemented a ban akin to the generation six ban to each gen, dealing with multiple BP users per team, it would only cover some of the issues (the various forms of quick-pass you see in current ORAS OU and SmashPass in BW/ORAS would still remain unaffected). Given the above, I'll talk about what I believe to be the best specific solutions for each generation's baton pass problem, or lack thereof, but I'll stay within areas which I have sufficient knowledge (BW and ORAS).
I'll start with BW. As the OP states, BW has two forms of BP for the most part - Smash Pass and Full BP. Both of these are as effective as they are primarily because of Espeon gaining access to Magic Bounce, which gets in the way of most counterplay to BP that was present in previous generations. With this taken into consideration, I'll first give my input as to if I think they're banworthy or not and then state the best solution, in my opinion.
Smash Pass is potent and only needs a safe turn or two, which isn't hard to get given the fact that screens will usually be up, and then you've got a mixrach or a mixmence with +2/+2/+2 in while your opponent is likely lacking a way to stop this pokemon from sweeping. I am not for just picking an example up and saying "look how good it did, it must be broken", but if a strategy is consistently successful and the opponent doesn't stand much of a chance so often, then you have to draw a line at some point - going onto some examples of smash pass that I feel speak volumes about its success: Shake won a BW OU live tour using Smash Pass every round (I even got two crits vs him in finals, but still managed to lose to his mence in the long run although I could have played a bit differently had I known all of the sets while another competent BW player, Leftiez, wasn't able to do much vs SmashPass either, despite having a solid team and playing around the first Shell Smasher) and the game linked in the OP of Omfuga vs Shake for BW Cup, where Omfuga used a standard Moltres rain team I gave him (he even slapped Haze onto Scarf Politoed, but you'll see more about this later in my post), shows Smash Pass dominating a semi-standard team archetype. There are infinite examples thanks to various people using Smash Pass to great success in Smogon Tour, Classic, etc. and I think that a strategy that leaves so little room for counterplay and minimal room for error whatsoever when playing against is not a competitive strategy, nor one that is healthy for the metagame. Furthermore, I think that Smash Pass needs to be addressed in BW.
How should it be addressed? The most direct solution is a ban of Baton Pass + Shell Smash in the same moveset (which was stated as an option in the OP). Going back to the purpose of this thread that I listed at the start of my post, this ban would put an end to the strategy that is banworthy while not having any effects on other strategies. This sort of specific complex ban has provoked a lot of fuss over the years because it's unprecedented in some areas and the justification behind it is shaky, but if we can limit the number of users with baton pass on a given team (which we did in generation six), then I see no reason why we can't go further and restrict movesets that we deem broken (such as BP + SS) as it would be sort of an arbitrary stoppage point to limit potential bans to number of users on a team when moveset bans would provide a direct solution to this problem.
Full BP is a whole other can of worms. I'm going to jump right into showing how hard it is to deal with it by referring back to the Omfuga vs Shake series for BW Cup, except using a different game, where Shake uses full BP instead of Smash Pass while Omfuga uses the same team, but this time Haze Politoed gets a use, but Omfuga still stands no chance bar a few extra opportunities to land a well-timed crit. To beat full BP, odds are you're going to need to continuously apply offensive pressure to your opponent and either crit at the right time or out-sweep them early and quickly, before it's too late and Espeon is sweeping you with Stored Power as you say "fuck pokemon" and eventually rage quit on your opponent haha. Going back to the main topic, full BP with no limits on the amount of BP users has the ability to adapt to normal counterplay and win a devastatingly high proportion of tour games it's used in (Espeon, a staple on these teams, has a win percentage of 65% in BW2 OU Smogon tour games this season and I bet it's even higher than that when being used on full BP because the rare occurance of seeing Espeon on a sun team and Espeon is also on SmashPass, which has a less reliable/consistent win rate). Before you ask 'why not just get rid of Espeon', I was just using it as an example as it's on every full BP team and it's pretty symbolic of the full BP archetype; there are better bans that wouldn't compromise a pokemon that has (albeit minimal) other uses. Anyway, the point of this is that full Baton Pass is nearly unbeatable using a lot of bulkier/slower paced teams and even when you're using something with a win condition or two and lots of offensive pressure, you have to execute perfectly in a short period of time just to have a shot to break through BP (you may still need to catch a lucky break to beat it depending on circumstances). Allowing a strategy with this capability isn't something anyone should want, so I'd think that bp deserves to be addressed in BW.
How should it be addressed? The solution that eliminates the current state of BP while not compromising any current outstanding strategies would be limiting the amount of BP users, similar to what is done in generation six and what is proposed in the OP, but I'm not sure if it should be to one or two users or what - that's trivial at this point, what matters is that the amount of users should be limited and once that's established, then the specific amount can be discussed if it's up for question.
Now onto ORAS. I know that Smash Pass is a thing in ORAS (that team with Whimsicott, Mega Diancie, Azelf, Gorebyss, Lucario, and Lando (before it was banned, idk what replaces it now)) and I've seen it in use before, but I honestly haven't played against it once (thankfully) and haven't seen it too many times to feel comfortable commenting, although the replays in the OP seem to be pretty indicative of how it is as a strategy. Regardless, to be fair and not risk misrepresenting ORAS SmashPass, I'll refrain from commenting on it for now. However, I will leave my thoughts on this GeoPass that was created, popularized, and abused to death after the baton pass limit was implemented. Essentially, it sets up screens, gets a memento off, usually gets a tailwind off, and then passed a Geomancy to an Espeon which is essentially invincible unless you have one of a very select few things or you manage to sweep the GeoPass team before it gets these conditions and the Geomancy up. The systematic and consistent success of this style just attests to the overall problematic nature of Baton Pass variants dating back to BW and still lasting today. It's actually a bit harder to argue for this GeoPass to be considered broken, when looking at it in perspective, as it does require a lot of support in the screens, memento, and tailwind, but they all are set up in order and the pokemon are essentually suicide mons to lead up to the sweep, so it's not really physical support, more like any other team member that synergizes well with a win condition, I suppose. Regardless, this archetype, like BW smash pass, will get the job done against passive teams that cannot get in the way of the supporters and eventual GeoPass to Espeon while still doing well against offense as memento and screens interfere with their immediate attempts to sweep and if the game gets prolonged, offense will eventually lose to espeon with a geomancy unless there is one of the few ways to prevent Smeargle from setting up despite having sash, screens, memento momentum, etc. I'd also like to point out the Smogon Tour usage stats again - Smeargle has a 71% win rate and Espeon has a 60% win rate (probably higher on GeoPass as Smeargle's restricted to this archetype as far as I know and it sits 11% higher, but can't say for sure). Smeargle's rate is absurdly high for a 'gimmick' pokemon that only has viability on one archetype, so it's fair to say that this variant of BP should go given this piece of evidence and the systematic nature of it that I mentioned before (Screens+TWind+Memento leads to Geo+Pass leads to death).
How should it be addressed? Banning the move Geomancy is the best way to go as nothing in OU uses Geomancy, it's the root of the problem given that it is being passed, and there was another move ban this generation, there's at least a slight precedent for it (although Geomancy and Swagger aren't really comparable, there's at least some justification and this is another solution that eliminates the problem without compromising any viable strategies, which I'm trying to emphasize here).
Overall, I generally agree with the OP's proposals for dealing with these issues and given my analysis of the various styles I discussed, I'm leaning to the side that these specific variants of BP are banworthy.