Separate Hot Water / Heating

[John Matthews]

Ok, so any suggestions on how best to solve these issues:

This property is a triplex (maybe quad with an efficiency), converted from a SFR, so it's got one hot water heater for the whole building, and one temperature control (hot water / steam radiant heating) for the whole building located in the second unit.

I'm thinking the cheapest way to provide enough hot water to the whole building is to replace the hot water heater with a 200 first hour rating hot water heater so I don't have to mess with the plumbing too much.

For the heat, I don't know if it's easy enough to separate the heat out to each unit, if not, my thought was to just leave the temp at say 62, and not give them access to the temp control, and let them get space heaters to make up the difference. The other thought is I could give them all control of the thermostat, leave it in the common area, and let them all collectively set the temp, but that seems like a recipe for war. A third thought is to just put in electric baseboard heaters in each unit, and either let it work in tandem with the existing radiant heating, or just shut that off entirely.

Anyone have any suggestions?