I'm going to quote a few things from Brawl Minus's main website.
"Brawl- has as one of the first and foremost goals, "fairness". That is, no character should be overpowered, and no character should be underpowered. We don't want another Street Fighter 2 where there is one character who kicks the crap out of everyone else."
"We will try to balance everything by taking everyone and putting them all on the level of, approximately, Akuma from street fighter 2 turbo. Expect crazy action and moves you may never have seen before."
Going by these quotes, making Pichu deliberately inferior to Pikachu goes against the intended goals of the project. He should be as good as anyone else, joke character or not.