Good videos
The only substantive point on which I think we diverge is that you seem to see an independent AI running the world or at least having it's own autonomy within it. I see us as being much more tightly coupled.
On the "trivial" question of which avatar is in command, that's a relatively simple authentication issue. Only one controls the master key set (which authorizes anything in "my" name). There are, of course, contingency plans for dealing with the accidental destruction of the master set but they begin with the AI determining that the holder of the master set is no longer functioning.
This is similar to the proposals I have for managing my anonymous - where (obviously) only the owner of the ID card can be allowed access to their own data but you must have a plan to deal with the death or disability of the owner. Typically we would use a "distributed key escrow" system where the owner would issue partial key sets to a number of trusted 3rd parties (relatives, lawyers, doctors etc) a majority of whom must collaborate in order to reassemble a working key set. If they attempt to do that while the owner is still alive, a Strong Revocation protocol both reveals and blocks further attempts.