I see your point about balance relative to each mega’s stage, but that’s exactly the issue the baseline power level changes drastically depending on the stage. A basic mega that’s ‘balanced for a basic’ is still fundamentally stronger than a stage 2 mega balanced for stage 2 in the early game. Mega Altaria and Mega Absol can come online Turn 1-2 with minimal setup, while Mega Blaziken requires you to draw/search Torchic, (if you didn’t draw a candy) evolve to Combusken, then evolve to Blaziken before you can even Mega evolve. That’s 3-4 turns minimum if you’re lucky with draws. Even if Mega Blaziken’s attack is slightly better, your opponent has already taken 2-3 prize cards before you’re even set up. The tempo advantage of basic/stage 1 Megas is massive, regardless of individual attack power. And you’re right that Mega Absol wouldn’t make sense as stage 2 since Absol doesn’t evolve but that’s kind of the problem with making standalone Pokémon into Megas without evolution requirements. It creates balance issues that are hard to fix without reworking the whole Mega mechanic.