So, you are talking about something like an AI-driven exocortex? Extending your mind with machine intelligence that is directly (or indirectly) linked to your brain?
What I am wondering about is neuroplasticity. Shouldn’t it suffice to provide the brain with direct connections to an avatar control system, because the brain can figure out how to operate it on its own? After all, the brain learned how to operate the human body on its own (there may be some “pre-programming” or “pre-disposition” present, but I don’t think it amounts to very much). Why shouldn’t it be able to control more than the human body (well, yeah, probably not too much at once)?
The point of view problem is interesting. I imagine it’s similar to the problem of having two eyes, each of which provides a 2d picture. Together they are interpreted in a way that generates a 3d impression of the space around you. Having multiple viewpoints in different realities would be quite irritating, but I guess once you get used to it, it would feel as if you had a more complete view on the world at large.