Pretty much what I wanted to say but kept deleting my posts before posting because I'm goin' through this phase where everything I seem to say comes across as harsh, asshole-ish and generally negative (I'm workin' on it!). Doesn't modern Yoseikan aikido (or "Yoseikan Budo," to be technical, I guess?) have separate aikido, karate and judo as part of their composite system?

Likewise, as far as my exposure to some modern arts like MMA are the mish-mash of boxing, bjj and muay thai training done together. One could hardly argue the quality, depending on your measure of that, of the martial ability coming from the good modern mixed martial arts (!!! it's almost like it's right there in the name) schools today.

All of this suggestion of "get a black belt in (whatever)" I find a little strange. Sure, the belt does great things .. holds my pants up, helps hold the dogi jacket closed.. but people should do their own thing if it's working. If OP finds it useful, what's the big deal? If not, and plenty of people don't find it useful, ditch it.

And like you said, it was pretty much the norm in Ueshiba's day if we go back and look at the history of those guys and what was required to become a student and what their general approaches to practice were. Has anybody studied the backgrounds of some of their cherished pre- and post-war "aikido greats," I wonder? What was Shoji Nishio (among others, he's just the one at the forefront of my mind for all his cross training during his Aikikai days and the influence it had on what would become his distinctive and arguably very successful "style") doing while he was and before he was training aikido at Honbu in the '50s and '60s?