This is a well-written post, and certainly the most eloquent argument in favor of a ban on Baton Pass yet - that it will become a problem in the future, and thus, we should act preemptively to deal with it before it becomes an issue. However, I disagree on a fundamental level about the properties of uncompetitive strategies and at what point they should be deemed banworthy.
We discussed this on Discord yesterday, but I feel the conversation is worth carrying on here. I posited that the current metagame, despite all the complaints, is in fact healthy because a large variety of playstyles are viable. You responded that balance is weak, which is true, and a polarized metagame with a lot of hyper offense and stall is not healthy. I then argued that the weakness of balance had little to do with its ability to win any given match, but rather that it was much more likely to lose to a weaker opponent, as the playstyle is less forcing than offense, which can dictate momentum in the hands of a skilled player, and stall, which can outlast nearly anything with perfect play. This combined with PRO heavily punishing losses to weak players, I argued, is the reason for the poor state of classic balance on ladder.
I have a unique and biased perspective on Baton Pass. After all, I built the infamous team that got us here in the first place: https://pokepast.es/6563a3fc106521a2 . Everything that follows is about that team specifically and some quirks that may or may not have been covered by others in this thread already.
Firstly, this team was built to be uncompetitive. All of my teams are. Not attempting to limit counterplay is, simply put, a teambuilding mistake. The more chances you give your opponent to play the game, the more chances your opponent has to win. With this in mind, it easily capitalizes on small mistakes from offensive teams, and will never lose to a team that does not have answers nor offensive pressure in competent hands. The most important turn for Baton Pass is Team Preview - against offense, lines ten turns deep can easily be precisely calculated, and forced wins against poorly-constructed teams can be evident from turn 0 and carried out. This certainly sounds broken and banworthy, doesn't it? However, the very predictability which allows a Baton Pass player to take over and annihilate weaker players without concern also makes the team subpar against good players. A good opponent can easily identify the Baton Pass player's win condition on the other side of the board and utterly deny it with minimal preparation - for example, keeping Clefable at above 90% HP so that Manaphy can never get through, barring an errant Ice Beam freeze or critical hit. Ultimately, Baton Pass is another style of Hyper Offense - one that trades off power against other offensive teams for a slightly better balance matchup and dominance against the unprepared.
Secondly, the team struggles against some very common threats. Clefable, obviously, can shut down the team's 'uncompetitive' gameplan on its own, forcing it to play like conventional offense until it is eliminated or sufficiently weakened. Ferrothorn can only be handled by Lucario or Flamethrower Togekiss, and Lucario can be worn down very easily, especially if it is played with Garchomp as a partner. The team plays no hazard control, so Stealth Rock makes its life much more difficult. It struggles, as previously mentioned, against offensive teams in general, as it is difficult to dictate your gameplan against a faster team. Contrary to popular belief, however, Rain is a favorable matchup for Baton Pass - Kingdra can be traded off with Garchomp's Sash and generally cannot come in on any attacks, making it easier for a skilled Baton Pass player to set up checkmate than a comparable Rain player. The team has no switch-in to the common Gengar, and must attempt to sweep first if confronted by it. With perfect play, Baton Pass simply does not beat common builds of Stall, such as this frankly less competitive team: https://pokepast.es/bce1e153e8df21b4 (indeed, this team was built after two frustrating games against Gengar on Baton Pass), as it can never get through a healthy Clefable without extreme luck.
Thirdly, Baton Pass is not easy to play. It requires accurate calculation from Team Preview and, at the very least, a fundamental understanding of how the team works. Failure to identify your win condition in Team Preview is tantamount to losing. For example, leading Scolipede is almost always a mistake - if you do not win on the spot, you've given over two turns to your opponent while making no threats (Protect and Baton Pass), which your opponent can use more effectively - for example, by setting Stealth Rock and dealing significant damage to the Baton Pass recipient. Baton Pass's broken mechanics turn some otherwise forced wins into 50/50s. My own winrate the first season I played this team was quite abysmal, and I would expect similar for most others.
Lastly, it must be considered how far we are willing to go to defend a qualitative standard of 'competitiveness'. Anything involving luck is, by definition, uncompetitive - cheapening the value of prediction. OHKO moves are banned for that reason, but what about Focus Blast? Serene Grace? King's Rock? Air Slash? Hydro Pump? I've even lost to a Shadow Ball SpD drop in the past, should that be banned? If beating unprepared teams consistently is an issue, we must take a serious look at stall, which is capable of posting 90%+ winrates in the right hands, simply because there is nothing to be done unless the stall player makes a mistake or the opponent is explicitly prepared. I, personally, do not think the state of stall is an issue - in the same vein, I do not think Baton Pass beating unprepared players is an issue. Neither Baton Pass nor stall has forced an archetype out of the metagame - instead, both have demanded minor adjustments to contest them, which is in no way unhealthy.
Now, will Baton Pass be unhealthy in the future? Almost certainly, yes. Substitute, Magearna, Necrozma, and Z-Crystals, and a working Baton Pass will remove the necessity of carefully removing counters and weakening checks, and at that point, something will have to go. However, banning it now would be tantamount to banning Salamence because of Salamencite, or Mew because of Mewnium Z.
This is the wrong time and place for a Baton Pass ban, and there are far more powerful threats to address if there is truly a desire to shatter a healthy metagame using executive action because it is boring. There are still so many facets of this metagame that are insufficiently explored...