as per https://bugzilla.redhat.com/show_bug.cgi?id=1122081 , anne mulhern was unable to 'convert' an issue from being nominated as a blocker to being nominated as an FE - it wound up being nominated as both. it should be possible to convert among all possible states. "nominated as both" is technically viable, but should probably be simplified to "nominated as blocker", because we usually consider blockers as FEs if we reject them as blockers. so we probably only need two states.