I don't think I've heard any good arguments against a point Ellis made in HIPS that "aiki" is a relatively new name for a concept that was fairly well understood inside many koryu systems that contained jujutsu / yawara in their syllabi.
Takeda was a guy who was good at it. He had a number of other skills as well. Whether he created from whole cloth or revitalized Daito Ryu, in my opinion, he was not creating an art for the purpose of studying aiki. Aiki was a high-level, inner teaching. He saved the good stuff for a small group of individuals, right? So it wasn't as if he was trying to get the world to study it.
Ueshiba, I think, did make an effort to distill the study of aiki for its own sake. Living though massive epochal change and connecting with really far-out seeker types, I think, convinced him that this stuff he could do that was special could bring about something desirable if disseminated. At least after the war was lost.
So while it is true that Takeda was Ueshiba's teacher, I really don't think he would be happy to see the way of aiki become a martial art trained all over the world.
What's the difference between jujutsu and yawara?
The late Zen teacher Taisen Deshimaru Roshi studied yawara and has written encouraging words on aikido.