Just want to clarify here... Have you checked with Saotome Sensei on this? Because I'm pretty confident that he sees aiki as the core of his art. (Which is, after all, called AIKIdo.)
Speaking for myself, I'm also not sure that I would agree that "aiki" and "internal strength" are the same thing. Certainly internal strength is an *aspect* of aiki, but (re)discovering internal strength wasn't Ueshiba Sensei's great insight.
I'm sure you're aware of the distinction that we make, but in the context of what we are doing there is absolutly a distinction between Internal Power and Aiki - but Aiki is dependent upon Internal Power, so...no Internal Power, no Aiki.