Man, I gave a try to CAT…
OMG… I suck on it in term of productivity, the rigging is not that bad (to be sincere, it’s more flexible than Biped), but on animating… I felt as handcuffed!
That FKIK switch on feets is a nightmare, the copyposes works, but I’m adicted to my “already done” pose collections.
Your suggestion looks like the only way to integrate Biped on Character Production Pipeline, but a 2 times rig per character/skeleton model…
CAT looks more like an “artistic animation” tool than a “produce as crazy” one, if not used to Physique I would migrate to Maya. 
Anyway, thanks by your tip. 