[gentoo-science] Question before setting up sage-on-gentoo

[JC D]

Hi!I want to install sage-on-gentoo using gentoo_prefix on a Mac OS 10.10.My first try was not successful and it seems it was related to the "kind of outdated" gcc-apple compiler that is originally used in gentoo_prefix on Mac.
I have a question: Would it be possible to install a more recent gcc such as gcc-4.8 (as soon as it is unmasked) and then build the whole sage-on-gentoo with this compiler, but keeping the rest untouched?
And how could I do this? Would it be possible to set up layman using the gcc-4.8 for everything in the overlay or could I use /etc/portage/env for that? 
Best regards from a newbie