I strongly agree with everything stated, Tera in it's current form is too unpredictable, which makes the metagame unhealthy.
There is no mind game involved at all. Sure, for example Annihilape usually run tera Water, but some people are also using tera Dark to bait people, so you have to cover Ghost/Fighting + Water + Dark at the same time, otherwise you have a high chance it can either setup in your face (especially if you are choice locked) or kill you with Rage Fist boosted.
Therefore, I would say showing the tera type at preview is the more healthy nerf, because it creates actual mind game = You know what tera type to expect, but the opponent can bait it as well because he's holding it.
It's clear that something needs to be done regarding tera either way.
Ageed, Terastallization kind of breaks logic, I look at it like a crutch. Don't forget Annihilape will sometimes also run Tera Typa Normal so it doesn't get hit by other Ghosts and continues to Bulk Up Resto Chesto.
I'm very passionate about how I feel about Terastallization as a whole from day 1 when it was first introduced on Pokémon Showdown, I was like "This is broken, not much skill involved aside from deciding when to use it". It's only base level Pokémon knowledge, I'm going to give this Pokémon a defensive Tera because it is weak to (THIS TYPE) naturally, and I really want to abuse the STAB boost of (THIS MOVE), so let me use it as an offensive Tera since I know it won't 2HKO unless it gets the 1.5x STAB boost which I can do with a click of a button.
If I do gain the privilege to vote for suspect testing of Terastallization I will be voting to 100% for tiering action (on Terastallization) the metagame at it's current state is quite unbalanced.
Outright ban (Terastallization will no longer be usable in SV OU) - I'm leaning with an outright ban, it's manageable as a mechanic (not saying it isn't broken) but you can get away with winning a couple of games / laddering high but I think down the line regardless of the nerfs below it won't be enough you'll have certain games where the mechanic itself especially from an offensive perspective will blow the game.
The idea of changing your Pokémon's type into a different pure type while retaining your Pokémon's original typing and having 2 different STAB boosts is a lot variables to prepare for. If you wanted a free Adaptability boost you can just Teratilise into the same type as your Pokémon. Going to the option route of having a free Adaptability boost on a Pokémon that already has a high attacking stat in my opinion could be overwhelming to handle (You see it with Chi-Yu quite often) it becomes hard to check for, you'll probably have to sack one of your Pokémon at least half of the time depending on the team matchup.
1 Tera user per team (Only the first member of your party will be allowed to Terastallize during the course of the battle) - This is my 2nd option of where I'm leaning, it's a solid nerf and the only one out of the nerfs I see working long term. You only have to focus on 1 Pokémon instead of 6.
Reveal Tera type at team preview (Any Pokemon can Terastallize, but the type they would do so into is disclosed at team preview prior to a battle) - (3rd Option) I like this as well and I do think it'll make a difference but still allows the user to abuse Terastallization, now you're just doing it while opponent see's it coming, ultimately I think if this is chosen, it won't be the last suspect test for Terastallization.
Only STAB Tera types allowed (Any Pokémon can Terastallize, but they may only do so to types that match their initial STAB typings) - Least favorite option, because it still gives the adaptability issue with all the Pokémon who abuse it like Chi-Yu, Dragapult, and Gholdengo. I believe if this is the option that gets chosen, it will force a lot of Pokémon to seem way more broken than they actually are. Tera will be used for only offensive utility at this point, which I can deal with but like echoed above by other users Offensive Tera Type Utilization is the REAL problem.