The only thing that I don’t like about them is the lack of a hard wired thermostat, I worry tenants could lose the remote.

The heat flowing to the radiator could only be manually turned on or off at the shut-off valve; there was no thermostat control in the apartment or bedroom to stop or regulate the heat into the radiator when the room reached a set temperature.Father was convicted of child abuse. 

. - Install two new high efficiency condensing boilers, and update windows and insulation for better heat loss performance.PROS - a) minimally invasive; b) can provide 15-30% reduction in heating costs (we are told).CONS - a)total gas expense is still paid by the landlord; b) individual units won't have individual control (except for a thermostat controlled shutoff valve for heat/water in each unit); c) AC would be available on with in wall/window units. 2) Try to individually meter each units' gas and provide each with a traditional forced air heating/cooling system.PROS: a)gas expense could be completely removed for landlord (huge)- even tankless hot water could be installed in each unit; b) each unit would have their own climate control.CONS: a) constructions costs of running new gas lines and soffiting sheet metal duct work. b) highly invasive with collateral construction costs; c) future costs of maintenance on multiple systems vs a single building-wide system. 3) An electric based heating system- This is tricky in my mind because of the high cost of electric heat.

The last owner provided the tenants hot water radiator heat via a single thermostat for the building that he controlled in his unit. 

You could do different levels of packages that can include anything from a Google home/Alexa, Nest thermostat, wifi security camera doorbell, smart padlock, smart outlets and lightbulbs, etc.

The whole house is heated by a boiler with radiators throughout the home, with the thermostat currently in the basement.

Take all programmable thermostats out of setback mode and set on a permanent HOLD.3.

Smart thermostats?

for example, if we send someone out for a heater repair, but it was due to a battery in the thermostat... we charge the tenant. 

The plan is to put in a Nest, or similar, thermostat in the whole way (under a lock and key) so to be able to control the temperature from wherever.