I might be splitting hairs, but couldn't this depend a little on how we look at it? If his overarching goal was to come into accord with kamisama, and this was a way of doing that couldn't we say the building of power was a means to this end? ...That the entire thrust of his actions (which includes the solo regimen) were about realizing a kind of Heaven on Earth?
Might it not be a fair suggestion that O Sensei was more concerned with realizing the purposes of kamisama than of building power? And that this is reflected in how he taught and allowed his students to then teach?
It's worth splitting hairs on this subject, I believe. But we have to split them as finely as we can and I notice a distinct split between Ueshiba's "purpose of the kamisama" and the general, vague pursuit of "universal love" espoused by so many who have no power.
Best to you.