Using Xiaomi temperature sensor as thermostate to control Homematic TRV

Hi all,
I am running the RaspberryMatic in my HA installation and currently I have got 5 HMIP-eTRV-2 thermostates installed in 4 rooms.
In addition I have got Xiaomi Zigbee temperature/humidity sensors in those rooms.

In general I have set up a nice multi room heating system which turns on the boiler (a TOON thermostate) as soon as any of those rooms becomes too cold. Right now the condition that needs to be met is that the (Xiaomi) temperature needs to be lower than the (HMIP) set temperature. This works well - in theory.
However, this will definitely fail in the long run because the TRVs will heat up and will have quite an offset to the Xiaomi measurements, closing the valves while still keeping the boild and pump running. The measured temperature difference between the Xiaomis and the TRVs is not constant so even setting an offset temperature (of max 3.5°C) will not work, I think.

So I had the idea to somehow use the Xiaomi measured temperature instead of the one that is measured in the TRV - just as a HMIP wall thermostate would do.

I don’t know if I started going down the correct route and would like to ask for your ideas/ input.

So far I have created a system variable in RaspberryMatic and an automation in HA which sends the Xiaomi measured temperature into this variable.
This is the code:

- id: '1650988768441'
  alias: Set Office Homematic Current Temperature from Xiaomi
  description: ''
  trigger:
  - platform: state
    entity_id: sensor.office_temperature
  condition: []
  action:
  - service: homematicip_local.set_variable_value
    data_template:
      entity_id: homematicip_local.homematic_ip_local
      name: OfficeCurrentTemp
      value: "{{states('sensor.office_temperature')|float}}"
  mode: single

So now I have got this value in RaspberryMatic.

But what next?

I read something about setting up virtual devices using CUxD. Would that be the right way?
In this case, I would aim at setting up a virtual wall thermostate, get the current value from the system variable (rather than the temperature that is measured at the TRV) and then create a group that contains the TRV and the virtual thermostat.

Or is there a more elegant way to achieve all this? Or does it just not work?

Thanks for your help,

Merc

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