Except that he says specifically and repeatedly that this is one of the goals of Aikido, which easily qualifies for your "shortcut to nirvana or union with God.".
I'm not sure how you get around that.
He didn't say anything about an "ultimate, divinely ordained path" - and neither did I.
I guess I never felt like Ueshiba thought aikido was a shortcut
, only one of many ways to a goal which many people (the majority of whom are not aikidoists) share. Maybe I am bringing my own bias to my reading of Ueshiba.
In any case, whatever "oneness with God" is, I think one would be hard pressed to show that an aikidoist is more likely to achieve it than anyone else.