No, no more Mew and Mewtwo plots, please. They've been overdone as it is. While they certainly would fit the theme, especially Mewtwo, I'd rather they just be regular legendaries encountered at the post end game. Maybe some villain NPCs will be searching for them or whatever, but I'd rather they don't have a big role in the plot. Besides, Mew would probably just be limited to being an event Pokemon as it has always has been.