Mike - bloody hell mate, that's a lot of thinking! Although you are very technically correct, I have to admit to having never thought about that before - if the airspace is there and, barring that particular rule, there are no other airmanship considerations precluding its use, I'd just go for it. Maybe that makes me a cowboy, I'd argue it actually makes me safer, so long as I'm not dangerously close to cloudbase and risking a confliction with anything descending out of the bottom.
As for following RCS instructions - you're still the captain of the aeroplane, and, as an instructor of mine would frequently say "air traffic are our servants" - but I'd have to have a bloody good reason to not follow their instructions, one that would probably either involve some form of aircraft emergency or the controller involved being about to have their ticket pulled!