You choose the next Megas

Incinaroar-Meowscarda-Intleon

Mewtwo Z and Mewtwo A

Mew

Garganacl and garchomp Z

Yveltle and Xerneas for dlc lore.

Starter trio: The Alolan Trio.

Legendary: Mega Mew and Mega Mewtwo Z

Mythical: Marshadow.

Ones I want: I already got my favorite with Mega Greninja, so I'll choose Espeon and Shedinja.

Lore Reasons: Breloom and Blood Moon Ursaluna.

Breloom because Mega Evolution can increase its spore production, turning it more mushroom-like.

Blood Moon Ursaluna because mega evolution can do a similar thing that it did for Drampa. It returns Ursaluna to its Hisuian youth while letting it keep its modern day powers.

There should be a Mega Mew.
Also, just a few days ago I noticed that Mega Absol's horn is shaped like the Mega Evolution symbol. Is that just me?