i had an idea that could work with this game not having megas, but still giving us the strategy megas give.
why can’t there be an item that, when held, gives the holder the ability (or abilities) that they’d have if they were mega?
Agree. Megas are something that need to get on PMU in my opinion. As a Gen 6 fan (We’re a near-extinct species =|), I still think the Mega stones themselves need to be in PMU as bag/held items, but I take what I can get. You got my vote! 
Some dungeons would change bosses to their respective Mega forms, like Mega Rayquaza in Sky Fortress - Sky Garden and-
Oh god 
(you still got my vote dw)