IMO so revision change/s of a package will be considered too Reproducible: Always
This can't be done blindly because other currently existing higher revisions might not work. Just think of a removed use flag. In the future emerge will uses >= atoms if the package is the latest existing version. See http://git.overlays.gentoo.org/gitweb/?p=proj/portage.git;a=commit;h=a531c670849d81edd15ba3e3ae820cbfe063db68
Of crap, sorry for fiddling with your bugs, I somehow thought this is about portage's --autounmask.
package no longer in tree