It amazes me that Revit does not have a good way of doing buildings that have repeating units (like multi-family residential or hotels). I envision something working similarly assemblies, but with the ability to change one and have it change all (like model groups). They need to be scheduled separately like assemblies, but be more stable than model groups. Right now different firms do a combination of model groups, linked models (one per unit type) or superfamilies. The problem is that the last two require you to leave your project to edit. At this point, the best solution would be to allow assemblies to be edited without creating a new assembly type if there is more than one instanced placed in the model.
I would love feedback from those of you who do more unit-driving work to comment on what you would like in this feature.