Interesting, makes me feel iffy about it. A bi-metal spring doesn't sound like a great way to control the temp. Bi-metal thermometers are REALLY slow, and can be grossly inaccurate, up to 50 degrees or more. I'm not trying to put the product down or anything, just trying to get a full grasp on it.
For a thermometer fast is good and wanted.
For butterfly valve control for this application, lightning-quick valve operation is not needed.
It would probably be too expensive and complicated, anyway.
Looking forward to the video.