in reply to
A "Perl-7" that I could actually USE right now
I think the Moose (and Moo and Mouse) devs are doing a brilliant job of wringing out performance and if I was one of those devs, I would find a general requirement like "25% more efficient" kinda insulting. If you want to dig, find bottlenecks and post them so that they can make their projects better, I'm sure they'd appreciate the hell out of that.
Ovid had a nice blog piece along the same lines -- renumbering 5.20.0 to 7.0.0 -- I think the general consensus was no. In that blog piece, there is talk about project Moe which may be what your after.