Well for myself I found compromise. Although in both proposals as I see you've omitted part where you'll discuss how you are going to implement this feature, implementing this feature as eclass addresses most of my concerns, since:
1. ebuild's syntax does not change 2. people will have to inherit some.eclass to use them and thus will do this only when it's really saves time/efforts I've dropped all other answers I was going to give you since I started to feel that this is just another cycle. We can discuss them off list if necessary. :) -- Peter.