Regarding Advance Wars: Or maybe that guy whose CO Ability is “Power of Money”? He could be a paid DLC character! …Ow! Stop hitting me!
Regarding Mega Man: Sakurai is right. Mega Man is special. There aren’t too many third party characters who can claim to be iconic of the NES (and part of the SNES) era… he is one of those few. Mega Man’s inclusion is absolutely appropriate; if you were to ask various people to list games they deeply enjoy from that era and contributed to the system’s success, the Mega Man franchise would probably come up several times. I don’t immediately plan to play as him, but I’m very glad he’s on the roster.