So apologies first of all.. great to see you've had a chance to build the replacement of the Stella-Z plugin you made.. sorry I've not been around much during its development to "help" but I've had a lot of health issues going on and automation in general has just been on the back burner..
However that said I've had an idea that I think we might've discussed back a few years ago.. would it be feasible to add a 'cooling' section for a separate device (i.e. an air conditioner) and be able to get your device to act as one single device? And then perhaps also fan control on top of that? So the case I have would be:
In my bedroom and living room I currently have 4 separate devices that Indigo can use for heating/cooling:
A TRV (in this case a Netatmo one but it could be any heat requesting device)
A fan (just a simple on/off job but theoretically could be a variable speed unit in the future)
An airconditioner (again at present just a simple on/off device but could theoretically be one with different set points in the future)
An independent temperature sensor in the middle of the room away from the radiator and air conditioners to get a better idea of the actual temp of the room)
Your plugin could take all 3 devices and be able to set heat/cool points and also control the fan.. so if I set the heat/cool point to say 20/22 if it became hotter than 22º it'd turn off the TRV and turn on the Air Con, then if it drops below 20º it'd turn off the air con and turn on the heating.. and perhaps some kind of logic to never turn the units on for less than X mins to stop the system from being worn out? And then through the power of the HomeKit Bridge plugin that could be presented to Homekit as one unified aircon/heating system rather than the mess of different devices I've currently got to deal with.
Go on.. you know this sounds exciting and you wanna do it.. go on.. go on.. go on.. go on..