There is truly nothing we can really do about that, (unless we introduce it incredibly late in the game/in the after game, which is a terrible idea anyways) simply because the vast majority of competitive teams, wether its built by some noob or one of the best known OU players, have a Mega Evolution on their team. I can agree with you now that it is to early simply because not everything is full evolved yet, but I still don't think we should have to wait for people to suggest these items. Also Mega Houndoom was BL for a bit but it was unbanned through a unanimous vote and almost dropped to RU this tier shift
Why not just stick LO and friends in the pokemart? They're important items that are going to be in every competitive team anyway, and sticking them in shops will allow us to assume the player has access to multiple copies of them (after all, no item clause, right?). I see nothing wrong with allowing shops to have choice items, LO, and lefties as soon as right after the second gym even. If LC can be balanced around these items, then surely they are balanced at the low 30s that we're going to be at after gym 2.