Thanks for the reply Garry!
Good to know that there is at least some possibility of automation here.
There is definitely a desire to keep some sort of “local temperature control”, although I realize that complicates matters (especially with only two wires to each stat)… and that’s why the heating has remained un-automated for so long! Do you have suggestions on how to go about doing local control?
I looked further at the Fast-Stat Common Maker product and it does seem like it would require a separate “common maker” at each stat, since it utilizes something they call a “sender”. The installation instructions say:
The Sender is the smaller component and has purple, white, and black wires. It is installed inside the wall behind the thermostat.
I also saw a reply in another thread that referenced Velbus “glass panel” controllers but not sure if there’s any way to use them in a 2-wire situation.