Heating is a complex topic and you should well be aware of the dependencies (also in terms of thermodynamics) and implications of changing components, and to speak frankly, it doesn’t really sound you are …
If you want to replace the loop control in underfloor heating, you either deploy a classic autonomous system to have inputs for temperature sensors or room thermostats, or you make OH take its place.
You need a smart plug (to power an electrically powered valve like these) and a OH temperature sensor per room. Then you need to program the valves to open/close in OH rules based on the temperature sensor’s input. Check out this post for a software framework.
But be aware that your heating will fail when OH fails, so ensure you have spare server HW and backups in place.
