You don't think that the meta will settle itself out to the point where there will be only 20 or so common terra sweepers that people will be able to recognize from team preview or team composition? I mean, who knows, they might go with the preview option and then 3 months later it'll be clear taht you were right and terra was broken, but personally, I would rather try to keep it than just give up on it right away. If we start running into situations where pokemon start getting banned left and right becasue their terra sets are too polarizing then we can safely say that terra is the issue, but we aren't there yet. All of the bans so far have been for non-terra reasons. Flutter got banned becuase it was too fast, too strong, had too good dual stab, and was too specially bulky. Hounstone got banned bc of last respects, Palafin got banned bc of the taunt set, and bundle got banned because of freeze dry + hydro 2 hit KOing the entire tier. Until we get to the point where pokemon become too centralizing specifically because they can abuse terra, I don't think there is a case for banning terra outright. You might think that the unpredictability itself is the issue, but I'd argue that's normal for a 2 week old metagame. Hell, I've been running around with brambleghast walling half of the physical attackers in the tier solely because people don't know it gets strength sap. Point being: it's too early to ban it outright. We need to give the meta time to adjust to common tera users. If it's 2 or 3 months from now and we've had ten pokemon banned because they abused terra typing too hard then I'll be the first to admit that terra was the issue, but until then I think Terra can have a place in the meta, we just need to have some time to figure it out.The main issue I have is that I cannot foresee any arrangement, even a combination of heaviest proposed restrictions such as typing revealed at preview+only Tera into natural typings, leading to an acceptable level of normalisation for Tera, nor a stable meta.
I still think, even under the strictest of arrangements, it is still incredibly flexible & unpredictable (posts by Askeia & others outline the Tera users' favour in so-called 50-50 scenarios perfectly) - this will lead to a meta in which there are too many options to prepare for & an unacceptable regularity of near-guesses, thus minimising the impact of a player's meta knowledge in building & play. Even under these conditions, it remains uncompetitive. Not only that, but allowing any Pokemon to have Adaptability for one STAB, is far-and-away above the power level we should be comfortable with, and will inevitably lead to an unhealthy meta.
Furthermore, Tera essentially sets the stage for the Meta to play out on, and confounds any sort of current & future necessary tiering action. With Tera still legal, in any form, it is impossible to disentangle any Pokemon from its interaction & dependency on Tera, barring obvious exceptions. This will lead to tiering nightmares.
Edit: response to almostgood