emerge -uvatD @world --newuse --with-bdeps=y --exclude firefox-bin::overlay_jl
emerge: error: Invalid Atom(s) in --exclude parameter: 'firefox-bin::overlay_jl' (only package names and slot atoms (with wildcards) allowed)
The rationale for the --exclude atom limitations is that we want to encourage people to use package.mask. Why don't use mask the package in /etc/portage/package.mask?
I don't think that supporting repos is a too bad idea.
Personally, I've never really liked "exclude", and think we should either make it properly useful, or just get rid of it and tell people to use package.mask.
Well, I see --exclude as easy 'please do not update/rebuild this right now'.
I'm sure some people find it useful. My point was that if we're going to have it, making it not suck isn't a bad idea.