Sure, but if the 997 GT3 RSR is relevant to this question, why then do the 997 GT3 and 997 GT3 RS not also share the same unit? After all (if I'm correct), the GT3 RS is the homologation model for the 997 GT3 RSR.
I think it's perhaps safer to assume that the 997 GT3 RSR exists the way it does precisely because of the specific rules that it was made to comply with.
Anyway, let's see. Maybe you're right and I will have to eat my words