Hey, I'm all about flippant answers so I'm down with that.
It just struck me that we have two terms -- kokyu ryokyu and ki ryokyu (for which we have a definition in standard usage) -- so we needn't double up. Kokyu ryokyu for ki power and ki ryokyu for will/spirit power. Nothing lost and everything doesn't become a hammer.
Just a thought.
Well, I still, for the fourth time, concede the "maybe", but "kokyu ryoku" is not understood by most people to be a subset of "ki ryoku" (not "ryokyu"), but rather as "breath power" or "timing". I'm perfectly happy with anyone translating "ki-ryoku" as "spirit" if they want. We all have to ante up.