Im not talking about "what if" situation. Baton Pass teams have an infinite amount of things they can substitute in place of certain mons, its not hard at all to find a new passer which might not be as good, but itll still work under the same uncompetetive premise as all previous iterations of Geopass. Its the same scenario as if we banned Excadrill (not even remotely saying drill is broken btw), people could use Sandslash, the only reason they didnt before said ban was because drill is better.
The fact remains that any team centered around baton passing to another mon (note by this that I
do not mean a single mon like Nastypass Celebi passing without any support like screens, memento, etc.) is inherently uncompetetive and completely based off team matchup. It doesnt matter who the passer is, Smeargle and Scolipede just happen to be the best. The "cleanest" solution, as you so eloquently put it, is not to have multiple suspects that each take roughly a month each time something new is discovered, its when theres a solution that removes any way of baton pass being broken. In the strictest terms, that's banning BP itself, but banning Boostpass has the exact same effect while only taking out the broken part of BP.
WebBowser The problem with that is that BPing stat boosts lets you come in with absolutely no damage, while a mon setting up by itself has to find a way to set up without losing all its health. The only time the situation you're referring to is correct is when another mon is boosting alongside you, which in a dedicated passing team situation, are dealt with by screens and memento if they start boosting straight away, or end up a turn behind because they have to switch in first.