I'm not too up to date on the latest news, but I guess this new mechanic would have some kind of limitations and it's not like you could transform any Pokémon into any type you want.
It wouldn't make any sense to have Tera Typing as a feature then if they disallowed you to Terastallize any Pokémon you want, as it wouldn't really be useful enough to give you an edge in battle and could simply result in some Pokémon getting special treatment, not unlike Mega Evolution. Based upon what we know thus far, any Pokémon caught in Pokémon Scarlet and Violet can transform into any type using the Terastal Phenomenon. Simply put, how this works is that each Pokémon can have any unique Tera Type, but to catch the Pokémon with the specific Tera Type you desire, it must be caught in Tera Raid battles. Countless combinations of Tera Types can exist for each Pokémon. Leakers have also said the ability to change a Pokémon's Tera Type also exists, (which I hope is true to make things easier for me), but this has yet to be confirmed. I have no reason to believe that this isn't true however, considering how much easier the developers made it for players to prepare their Pokémon for competitive play with Mints, Exp. Candies, Hyper Training, and so on. I admit that having to grind in Tera Raids over and over just to get the right Tera Type I need sounds extremely tedious. More information on it can be on Pokémon's official website in the link below.
https://scarletviolet.pokemon.com/en-us/news/terastal_phenomenon/
The real question is, what's gonna happen when I terastallize my Shedinja into Electric type and let it hold an air balloon? 😈
About turning Shedinja into an Electric-type and equipping it with an Air Balloon, sure it can make Shedinja harder to get rid of definitely and sounds like a lot of fun to try and troll unexpecting people (or even NPCs with), but nowhere near impossible to get rid of. It can still faint instantly from chip/residual damage from Burn, Poison, Curse, Stealth Rock, and so on, which nearly every team has in some form or fashion. In addition, it could still be hit by Pokémon with the ability Mold Breaker and all its clones or moves that have the ability to ignore abilities. Because of that, it just sounds too niche and gimmicky because it really only spells disaster for players that aren't prepared for it with really bad teams. I personally believe that it's a waste of a Tera Type. Personally, I much rather use a Fighting-type Tera Type on my Contrary Malamar to not only spam constant Superpowers, but also get STAB from it while boosting my stats.
I think this mechanic is pretty exciting, personally. Maybe I'm in the minority here but I felt like Dynamaxing was the best gimmick they've done so far, because even though the Mega Evolutions were cool I don't think they were necessarily balanced and they were only limited to certain Pokemon, and the Z-moves were just annoying to me. That being said, the little hat does look really dumb. I am just excited for the strategizing that will go along with being able to switch up the type of your Pokemon once per battle.
I agree with you about it being exciting and Dynamaxing. It was the best mechanic in my opinion as well. Mega Evolutions were way too broken, especially when you consider Mega Rayquaza and Primal Kyogre and Groudon. I have no clue what Game Freak was thinking when they designed that. However, broken Pokémon aside, the main issue I had with Mega Evolution was that only certain Pokémon were able to do it, which made it seem like certain Pokémon received special treatment. In addition, many Pokémon got Mega Evolutions that really didn't need either such as Beedrill, Pidgeot, Audino, and so on. Using those to Mega Evolve is, in my opinion, a waste of a Mega Evolution when other Pokémon could have been much better options such as the gen 2 starters, Flygon, Haxorus, and so on. Z-Moves weren't all bad because all Pokémon could use them and they definitely gave you an edge in battle when you needed it, but the problem was they wasted a held item slot and it was always hard to predict which one of the opponent's Pokémon was going to use a Z-Move at any given, making the game feel more luck based than it should. Dyamaxing was the best gimmick in my opinion because it could be used so strategically to not only deal massive damage, but to play defense as well and prevent yourself from losing at a crucial time. This new Tera Type mechanic seems like it could be just as good as Dynamaxing and with a little experience and common sense, you should be able to predict what certain Pokémon are more likely to Terastallize into.
