I've been pondering ideas for rooms helping with special missions and a couple preliminary ideas I have is a melon-pult which would do damage to the special mission enemies like melons do in team fights for those of us (like me) who struggle with special missions.
Another special mission related idea is the telephone room which would reduce the time in between resets of special missions for those that excel at them.
Another non-related idea from my teammate mahhafooznit is a battery depot room which would increase battery capacity and batteries available per day to use. A room capped at level 10 that gives +1 usable battery and +2 battery storage per level.