Like mentioned, its not as easy as you think it is. Many rigs and vertexes aren't perfect. Let's not even get into the details of how time consuming it is to perfect the animations and make movesets for characters. On top of all that, this mod is trying to be as professional as possible; as if you bought it from a store. We wouldn't want a character such as Mewtwo with Olimar sound effects. There are many areas that Brawl hacking hasn't covered yet.The number one olimar hack on brawl vault is cloud strife over olimar... So I'm pretty sure it is possible.
Also I would love to hear the ideas that have been thrown around about olimar... to make his play style more... exciting.
Edit: Olimar is staying. His moveset will still require pikmins.