"Closest" is really a red herring - I could argue that for a number of people from various points of view (and those people have indeed made those arguments). Anyway, my guess would be that he would have been in favor of the "outside-in" approach of building Aiki through repeated kata training - that approach favored his personality and his training situation. Of course, Ueshiba was known to teach different people in different ways.
My personal experience with him, and with some looking back in hindsight, would be that he had a lot of stuff, but probably lacked a way to explain the "universal field theory" behind what was going on, and that much of what he was doing and showing was influenced and restricted by his overwhelming desire to preserve the precise external form of his training as faithfully as possible (not a bad thing, but it has its drawbacks).
My teacher who spent seven years in Iwama as an uchi and soto deshi always said he felt kind of bad for Saito because he strove to maintain someone else's practice. I understood that and yet I can't say I agree at this point in time. I would almost thank him for it.
But your point is well taken.