One of the things I like in a Thermostat is to be able to tell it at what time I want a given temperature, and then it will start heating when needed. So a while earlier in deep winter than at the start of the heating season.
I think it is predictable with a 1st order approach/linear approach. While the system is not heating, we can observe how fast the temperature drops. And when the system is heating, we observe how fast it heats, and we can suppose that this is the speed for the current cold.
I think the “fall time” is sufficiently linear with -LossWatts and the “rise time” is sufficiently linear with HeatWatts-LossWatts=NetHeatWatts. Now when we know “NetHeatWatts” from the previous heat cycle, we can already get an idea of the time needed to heat from say 18°C to 20°C and therefore determine when to start heating to get 20°C at 6:30 for instance. It does not have to be precise to the second, a warm radiator is always nicer than a cold one, at the same temperature.
It’s not dead easy to do, but I think it’s doable.