Interesting theory, I would just have assumed that both of their madness and mantras come from just being driven insane from pain, not necessarily anything deeper realmatically. In most cases, I think, when the mind or something else "leaves" within the cosmere, it is gone for good, and can only be replaced by a "spiritual patch", (think Kaladin healing from a shardblade wound, his original arm in his spiritweb is replaced by something similar). If, say, the mind were to leave, I doubt it can be simply brought back with something else other than a fake, so Raoden returning and the other hoed healing without outside interference are likely impossible. That being said, it's got me thinking about the implications of this and Emperor's Soul, where the emperor's mind has departed and a new one must be made. This could be something similar to what you suggest, I think.