I don't think anyone has really used Drifblim in RU, I'm fine with him moving up.
Four proposals though: Escavalier Low S ---> Top A, Smeargle Top A ---> Low S, Magneton Top B ---> Low/mid A and Rhydon Low A ---> Top/mid B
Having a fair amount of experience with all 3 of the proposed pokemon, I find their placements here kinda odd.
Escavalier
Escavalier's placement in S was odd to me, as he is quite easily stopped in RU. With Durant being as popular as ever, Escavalier's main counter, Magneton, is rising up to be more popular, this makes many teams have a counter to Escavalier without even having him in mind. Now obviously Escavalier's power is ridiculous, but with base 20 he is out-sped by literally everything (without investing into speed or something, you could out-speed Slowking if you do I suppose) outside of trick room - which is what he is, a trick room sweeper. Being by far the best abuser of trick room in the tier, although come people could argue Slowking is, he is superb at what he does, however trick room is, in my opinion at least, the hardest play-style to build by far. If you form a core of Slowking and Escavalier you're doing well, but then again it is using trick room, it is the one of the only things Escavalier can do. The other strategy he uses is quite simply bulky offense. With very good base 105 defenses, he can withstand a fair amount of attacks. Without any kind of recovery, however, he is easily weakened and in many cases 1/2HKO'd by a powerful and faster opponent. Due to these down-falls, I believe Escavalier is too much of a liability for your team in too many matches to be S rank off of a trick room team, on a trick room team? That's a pure niche for him. "Reserved for the top threats in the RU metagame. These Pokemon are usually able to perform a variety of roles effectively, or can just do one extremely well with little to no extra support. Their use has low risk involved and high reward exerted. Pokemon in this tier have very few flaws that are patched up by numerous positive traits."
The bolded parts are precisely what Escavalier is now, and while it does say this pokemon can perform a role extremely well, it also says it needs to have little to no support, which Escavalier does not have. Escavalier is by no means a bad pokemon, otherwise I wouldn't be proposing top A, he just isn't worthy of S.
Smeragle? That's a completely different thing (I forgot the saying :/)
Smeargle
Smeragle is pretty much the most diverse pokemon of the tier. While most people stick to the standard hazard setting and baton passing sets, I like to experiment with Smeargle, and I have been very much surprised with what I have found. His standard sets are actually very good, being the only pokemon to get SR, spikes and toxic spikes without being set-up fodder thanks to learning whirlwind, and his baton pass sets are great because he can boost any move you want if your team lacks the move being present on it. Things that I have found great with Smeargle, however, is a tailwind utility set, a memento set (I know that you can use Uxie for that, but Smeargle is just as good really) and a couple other fairly niche sets, one of my favourites being a para-phazing destiny bond set, which spreads paralysis around your opponent's team and as soon as you're about to be killed you get a free kill on your opponent. It was really unexpected for my opponents and they simply failed to it, thanks to the paralysis being spread around he did get a KO almost every match - you gotta admit, for something that weak offensively, that's pretty good! The simple reason why I think he should be S, is his unexpected viability.
Magneton
Magneton, how versatile you are, which our analysis shows perfectly with a total of 4 sets with a decently sized 'other options' section as well. The reason why Magneton is viable in so many different ways is Magnezone. Let's be honest, Magneton didn't need an evolution, he was set with an incredible 120 base special attack, that for a tier like RU is even more incredible, but also got eviolite to make his bulk superb as well. This means that even on defensive sets he's going to hit your team hard, and on the offensive sets, well you better get ready to have your ass kicked. My personal favourite of Magneton's sets is a mix between the scarf magneton set and the steel killer. It has a massive amount of power, is fast enough to out-speed non-scarf Cinccino with a timid nature and promptly OHKO it, and like the other primary electric types of the tier (no electivire you don't count anyway) gets volt switch for more scouting opportunities. This sounds great and all, but why is Magneton not S rank worthy then? Well, he is frail without running an offensive set, and too slow when he is. This doesn't stop him being A rank worthy at all, and honestly I was just checking where Magneton was to see if he was in mid A or not, since I believe he belongs there so much. Can you really tell me that "Reserved for Pokemon who are slightly above average in the RU metagame. These Pokemon have more notable flaws than of those above it that affects how they function in the tier. Their positive traits still outshine their negatives, but they require a bit more team support to bring out their full potential"
Fits magneton better than:
"Reserved for Pokemon that are outstanding in the RU metagame and can sweep, wall, or support the majority of the tier. These Pokemon require less support than other Pokemon to be used effectively, but still perform less consistently than the average S rank Pokemon. A rank Pokemon have few flaws that can be overlooked when compared to their positive traits."
Thought not.
Rhydon
Rhydon does not perform as well as he logically could. He has good power, great physical defense and HP, but his speed leaves him susceptible to so many special attacks it simply doesn't work. I find him a massive under-performer on my teams, so he always gets replaced eventually. For me, he is either a fully defensive stealth rock setter who does little to nothing later in the game, or an offensive pokemon who dies too quickly. I have built whole teams around him yet still he fails. I can see why he is good, and I am sure that some people manage to use him, but as far as I have managed with him, naddah.