Hi,
I have two "old" TV, each one using a MiBox. These two TV are only used as monitor for the MiBox, they are not connected to anything else anymore as I can do anything I want through the MiBox (watch TV/Replay, Netflix, YouTube, Kodi, etc.).
They are not HDMI CEC compatible so I still need the original remote to turn the TV on and off. In fact it's the only thing I need the TV remote at all and it's a pain.
Is there some kind of power adaptor or power switch that takes in the HDMI signal to get the CEC command on/off to just switch on and off the power to a device through its power socket? Just like you have those kind of power switch controlled by remote or by smartphone to turn on/off lamps or whatever you want, but in this case controlled by the HDMI CEC commands from an AndroidTV box.
Maybe you can try using a google home compatible smart socket like TP-LINK, and issue voice commands to it via Mibox remote.
But I think Logitech harmony would be easier.