here's what Game Freak should do:
Retcon Eviolite so that it only works on Pokemon in regions where they can evolve
so like, you in real life are traveling region to region with each game that you play
say you find a new item native to Sinnoh in gen 4
Gligar evolves with that item
say that Eviolite existed in gen 3 for the sake of this example
In 3rd gen Hoenn and Kanto, Eviolite would not work with Gligar because you hadn't found the item yet
But in Sinnoh it will because you found the item needed to evolve it
And in Unova and Kalos and all future regions it will, because you "brought" the item with you
This theory works even better with location evolves
remakes kinda fuck with this, but remakes retcon everything already so...
It's slightly breaking the 4th wall, but it works. Works much better than megas, regarding adding new evos to past Pokemon.
