- Megaevolutions should have a risk or reason not to use them (for the sake of balance and strategy) Examples: Losing a turn, losing some HP while using it or moves use 2PP instead of one.
The negative to Mega Evolving is not having a useful hold item. Having no hold items (because the Mega stone is needed) eliminates several strategies off the bat that you could use a Mega Evolved Pokémon for. Because of their offensive stat increases, Mega Evolved Pokémon are reduced to being only sweepers. Any other use you may intend a Mega Pokémon for (including tanky types) is a waste because of the lack of a hold item. Even as Sweepers, Mega Pokémon may still be at a disadvantage because of the inability to use key sweeper hold items such as the Quick Claw or Scope Lens.
How i thought it would work was the Mega Evolution would occur when they got low health or something. --- If I learned anything from Avatar: The Last Airbender, its that if someone asks you a question, the best possible response is "A giant Lion Turtle."
All the megas have a BST of around 600, some with really good abilities too, so basically everone's gonna have one random legendary teir mon on their team. --- gat mi swaeg ohn, aint ekven gun tuch meh.