I think it would be very hard to disentangle Ueshiba's aiki from his spirituality/enlightenment. Ueshiba's spirituality, his spiritual ideology, is a tricky thing. Is it possible that his body skills are not necessary to his enlightenment? Of course. Is it probable? I really don't know. Once he was on the path of aiki, literally everything changed for Ueshiba.
Remember, he said, I am aiki. He said, this is how to do that with aiki. Aiki systematically alters and changes the physical body and also the mind on a fundamental level. Once that occurs, how can you disentangle it from whatever one does?
To even begin down that road is a lot of work and research. A lot. Much more than aiki training. Not that it can't be done. In fact, I think it'd be extremely interesting and valuable.
I would prefer that we be very careful around the term "aiki." From my experience in Japan, it appears that any activity can be considered a path to enlightenment, as long as it is followed with a certain intent. That being said, no activity that lacks this intent would get you there.
Does that make any sense?