Probably could, but thats messy and out of reach for most of the general public. I'd consider myself capable, and I still haven't done it despite wanting to.
I'd settle for appliances providing a standardised port for control/monitoring, that you can plug in your own ESP32 controller. Harder to sell to the general public.
Thats awesome, will keep that in mind for the next upgrade.
While we are shouting out cool projects, for Mitsubishi electric aircon: https://github.com/echavet/MitsubishiCN105ESPHome
There is also one for daiken, but I haven't directly tried it.