Universal is any hangar with all functions, common hangar have no special function. Craft have specified function he requires from hangar if none specified, it can fit anywhere. You can define your own functions so, that means space port is just a function, submarine pen is just another function. Small craft or big craft is just another function, unless you want to make 2x2 crafts for 3x3 hangars. That function is also requirement for crafting said craft. Moving crafts between hangars in the base will have to be done anyway. If a craft that can be in hangar A or B is in hangar A and you want to build craft that requires hangar A, the game either have to be smart enough to move said craft, or player needs a way to move the aircrafts manually. Still think the "ProvideBaseFunctionality" is logical way.