There have of course been thoughts along these lines before - example
Often, a blocker would be connectivity of the peripheral parts to the system host; maybe there is a unique controller as with zwave.
My own approach is a backup strategy. Replace host with any old laptop at a push.
All my peripherals are IP connected via various gateways, nothing is wired/wireless direct to the host.
Also designed in resilience - in case of host or network failure, of course lighting automation is lost. But there are still functional wallswitches.
If we apply the design-in principle here, you might choose thermostats that independently (locally) control the heaters. Openhab can add cleverness by adjusting setpoints, or working vents, alerting about faults,or whatever.
But if OH is lost, essential services continue to function at a basic level.