The return of balancing cards like Fluffy Berry and Double Rainbow Energy would actually be a very smart idea. Those effects demonstrated an attention to even the most minute details, a level of dedication to game design that has not been seen either before or since. Even the fourth generation block had its fair share of unhealthy cards. I believe this is one reason why the EX block format is becoming popular-at least compared to other retro formats-online.And if you get it wrong you end up with completely uncontrolled power creep across the board for years to come.
The point of my post wasn't to take "balance" the way you have, but to argue for a reduction of HP and HP caps across the board, not an increase. In terms of how you handle that given it'd be a step down from what came before;
- Hard format rotation to ensure the viability of the TCG as a long-term game. This would probably be unpopular, so the next best thing;
- Print more attacks that are specifically punitive against Pokémon V/VMAX/VSTAR but are not necessarily punitive against Pokémon ex. e.g. "If The Defending Pokémon is a Pokémon V, this attack does [some extra amount of damage]", various Trainer cards that punish players for having Pokémon V/etc in play. Then, once you've cleared the old format's multiprizers out, go after the multi-prizers of the current format. When multiprize cards originally debuted, there were a ton of cards with punitive "If the Defending Pokémon is Pokémon-ex..." attacks so that running Pokémon-ex really leaned into the entire idea of cost/benefit. People also forget multiprizers left the format for basically an entire generation, too, and there was an extended period of time where Lv.X cards were clunkier to get into play than Pokémon-ex (several Lv.X were de facto Stage 4 cards).
Generation 5, like it was a mess for the video games, was also a mess for the TCG, since it brought back multiprize cards in such a lousy, hamfisted way, and seems to have baked in the contemporary thinking that the only way to fix the game is to keep making numbers go up. Gen 3 (and Gen 4) TCG game balance is entirely different from what you are proposing.
Just to be clear, however, the idea Yangiku advocated above was to raise only one number; the HP of single prize Pokémon. Not the HP of anything else. Not the damage of anything period. Right now 200 damage seems to be what the average double prize Pokémon is capable of doing. Which means Pokémon is trying to balance the game so that stage 2 ex's can tank a couple of hits. Now, if you compare the old Arcanine ex to the new Arcanine ex, 250 damage has essentially become the threshold for "that mid-range, heavy-investment attack on a multiprize Pokémon." Essentially what 100 damage was during the EX era. Back in the EX era, there was about a 50 HP gap between Arcanine ex's attack and the maximum HP (discounting Wailord ex), just as there is about a 100 HP gap between the new Arcanine ex's attack and the maximum HP. The theory was to reestablish something closer to the previous ratio of damage-to-HP-to-stage-to-costs-to-prizes, freezing the highest numbers where they are and raising the lower numbers accordingly. However, you identified another really important piece of the puzzle when you pointed out the existence of cards balanced against the merits of Pokémon ex.
I'm only synthesizing what I've heard other people say. I'm guessing you and Yangiku have a much greater, first-hand knowledge of game design than I do. (I'm pretty sure Yangiku even has a college degree in that field, or at least has a strong professional interest.) This is reminding me of the time a discussion on the toxicity of Arceus, Dialga, and Palkia GX turned into a very thoughtful, analytical, critical analysis headed by a user named Otaku (whose subtitle is, ironically, "the wise fool?"). What started with several people (including me) ranting about the woes of the day led to a compilation of documentary-worthy material (starting near the top of page 2). You can find the discussion at the link below. This was back in early 2021, by the way, during the pandemic years, and the forums were far more turbulent then than they are now (which was one reason why I eventually quit the forums for a while). Perhaps some of you would be interested in reading?
https://www.pokebeach.com/forums/threads/vmaxes-adp-and-the-terrible-power-creep.151926/page-2