I think Faré's final point really gets to the nub of this issue: how worthwhile is it to have a CLEAN-OP, instead of having the user blow away their fasl cache manually?
My guess is that the answer is that it's most valuable for novices, who won't necessarily know where to find their caches.
The follow-up: is CLEAN-OP that necessary, given the cheapness of storage and the presence of a working (to the best of my knowledge) :FORCE argument to ASDF?
At any rate, I'd be happy to review and edit a proposed informal spec for CLEAN-OP with an eye to its implementation.
If no one's willing to take a poke at writing a half-page about how CLEAN-OP should work, I'm going to take that as a sign of weakness of demand.
Cheers, r