Well, I guess you are already self imposing a negative consequence of restricting yourself from using Math::GMP

No loss - there's an alternative ;-)
Probably doesn't help much if I want to install a module that requires Math::GMP specifically - but that hasn't happened.

Actually, I've just checked and the number of pre-requisites for Math-GMP-2.11 is now much reduced (courtesy of changes to TEST_REQUIRES that were made in 2.10), so I'll be able to resume installing it again without having to endure flaming nostrils and steaming ears.

Cheers,
Rob