Does desire for power help or impair the learning or operation of Aiki as O Sensei understood it?
Since I have not idea how O'Sensei understood it, I haven't a clue.
But, IMHO, from how I understand it, it would depend on the definition and intention of both "desire" and "power".
If "desire" is an egotistical attachment, then yes. If "desire" is a direction and a discipline, then perhaps no.
If "power" is over others, then yes. If "power" is over self, then perhaps no.