If I, say, hold someone with "aiki", I'm essentially using my 'jin' (I prefer that over kokyu because kokyu implies a bit more than just jin and it's unnecessary for this conversation) in accord with Uke's forces to effect the "aiki". The point though is that the "aiki" application is still based on the essential intent-directed jin/kokyu force. I.e, the basis of "aiki" is still going to be the ki forces or the kokyu forces (same thing for all practical purposes). "There are many jins but there is only one jin".
No argument there, but don't the Chinese say that someone "has" jin or doesn't "have" it? Since I've read that jin = li (muscular force) + qi (ki), it seems to me that it's something one has to create within oneself. Those who haven't done that work (or who don't even know of it) don't "have" jin, wouldn't you say? And since you pretty much equate jin with aiki, it seems reasonable to say someone "has" or "does not have" aiki.
What I'd really like is your comments on the tai chi ruler thread.