Why not? Falco may have been an established fighter pilot who prefers aerial combat, but Smash sees him largely as a hand-to-hand pugilist, who, when opting to use a vehicle, pilots a tank. And the reason for that is obviously so it would fit the framework of Fox, but I think the same can largely be said of Funky, who, should he be included, would most likely emulate DK. Often times powers in Smash eschew their typical functionality in the series of origin, my point is that some established characteristics do as well for the sake of the roster.
I also agree with your point though, Smash isn't really an "adventure" anyway, it's a fight. A fake fight among toys, if you want to justify it as Nintendo does. And if there's an adventure mode... just have him be reluctant. I'll again refer to Falco...
Adventurer or not, Funky's not a pacifist... dude likes competition and builds weapons...