IMHO, all techniques lend themselves to training aiki if you focus on the subtleties of connecting, blending, and taking balance. All waza can become kokyu-nage (breath/timing).
Well, I think if someone is smart, they might be able to make inroads to other modes of movement using only waza...
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?