I don't think you need temperature sensing to achieve what the author wants: you just need the amount of hot water mixed in to follow a specific non-linear curve. We just want to adjust sensitivity on an already-functional mechanism.

Given my understanding that water heaters are all calibrated for approximately 140°F, then even assuming some fudge factor it seems possible to do better with pressure-balanced valves than we have today. Especially if the valve could be calibrated at install time.