Since developers are already hacking eclasses to do that, it may be a good idea to just make it a standard. The concept for EAPI5: 1) every eclass will be sourced just once; 2) any future call of inherit() with the same name will only cause inherited eclasses listed to be reordered; 3) effective exported functions will be chosen from ones exported by last eclasses on the list (last passed to inherit rather than last sourced).
Rejected: http://www.gentoo.org/proj/en/council/meeting-logs/20140617-summary.txt
