The Hospital is a nice building which is completely left to its own devices. I like this suggestion very much! Maybe the defibs it sells could be on a rental or one-time use basis though, so as not to upset the price of the current ones in circulation.
I don't really know logically why the Medic and Armory NPCs are separate. Just give me one NPC to fully heal me or overcharge my health and armor, and this one with it to do this stuff.