Assist Trophy: Toad

I think before Toad becomes a character, he needs to be an assist trophy. He could just jump up and down saying "(insert character here) the princess is in another castle" and used as a distraction.

Assist Trophy: Rush

 Mega Man's sidekick deserves some action, but not enough to be a character just yet. Mega Man should start out solo, then maybe add Rush later. Rush could do a variety of moves at you, from turning into various machines to shooting at you like a rocket.