A reasonable alternative would be to have a separate variable in make.conf, such as ECLASS_OVERLAY_DIRS, which specifies acceptable overlays for eclasses.
In most cases, users would probably only have their own, local overlay there, and any eclasses found there should be used in preference to any in portage or in the overlay the ebuild came from, if applicable. Every time portage looks for an eclass, it should check there first (caching what it found, to save future lookups w/in that run) and just use anything it finds. -JimC -- James Cloos <cl...@jhcloos.com> OpenPGP: 1024D/ED7DAEA6
