I would have to say from that list that Megaman would have been a nice character.
In general though, the only thing that I really disliked about Brawl besides the internet being choppy through it, was that there was no obscure character that you could unlock. The inclusion of Marth and Roy springboarded the Fire Emblem series to a level of where it was better known. An Advance Wars character, a Custom Robo character (Ray Mk preferably), or hell even Saki Amamiya from Sin & Punishment should have been in. I mean if Nintendo did that, there would be better sales for the obscure games.