Most of the light switches in my house are wired up through Z-Wave. Those z-wave boxes are in the electrical box in-between the normal, everyday, traditional light switch and the power.
100% of the time, if i flip the switch a direction, it changes the state of the light. It never fails. Power just came back on? still works. Z-Wave controller down? Still works. Internet out? still works.
Then, I can "add on" automation using that zwave network to do things like turn lights on/off from my phone.
If anything were to cause issues, have bugs, have problems, etc... I can unplug the controller and it goes back to fully functioning light switches.
While I'm working on my own system similar to yours, and I'm designing around the same concept, most IoT manufacturers aren't. I get why people's default reaction to IoT stuff is to run away, because they are mostly very poorly designed.
The issue I see is that there are many things that are designed like that, but they often require professional installation or are significantly more expensive, which leads to many just getting the cheaper option which works in the best case scenario.
I think the easiest solution for now is to just keep my blinds open a bit more and just use the sun like people have been for thousands of years.
Then I realized I could just program my old one to turn on in the morning and evening when I am home on my set schedule. It works just fine, and I know enough to think that replacing it with a complicated machine-learning process might cost me more headache than occasionally turning the heat up.