I like this, but I don’t like that rooms are cold unless I hang out in them. I live in an old stone house and I’d rather have a room schedule than a room presence sensor.
I’ve done something similar. I use the excellent scheduler from Niels Faber. I have room radiator TRVs. I have a helper entity that counts the number of radiators that have an open valve, and an automation that triggers when this changes to/from zero. This automation adjusts the central nest thermostat, converting it to more or less a posh switch.
My radiator valves use Better Thermostat and external temperature sensors, and the whole thing keeps my house warm in every room. I need to write a GH blog post about it, but happy to answer questions/share bits of config