Well, I think if someone is smart, they might be able to make inroads to other modes of movement using only waza...theoretically...
over a loooooong period of time.
But why the hell would you do that if there's a direct way to train it, and the whole point of training the waza is to get the skill in the first place?
I think that is the single most compelling question out there. Rarely have I seen so much said in so few words.