Crash would be kind of cool to see in Smash, not one of my most wanted, but he's cool.
Also MMX Dive is getting Mega Man, Protoman, Roll, GBA Zero and Leviathan as playable characters at some point soon. This'd be the 4th version of Zero(Normal, Lab Coat, Black Zero and GBA). And Mega Man X has like 5 variatoins so far(Normal, Command Mission, Light Armor, Giga Armor and Ultimate Armor).
Given some of the leaks, we miiiiiiiight see Super Adapter Mega Man as well. Still nothing on Battle Network characters being playable, or any variants on Vile.
EDIT: Mega Man X is also supposed to have a Command Mission Ultimate Armor version and Iris from MMX4 are supposed to playable too. There's some bosses from MM5, X1 and Command Mission too.