Could a temp sensor/ throttle kickback be a useful tool for breaking in ABC 2-strokes using it to signal when the engine should be timed or such to be shut off to cool to give extra advantage of just relying on standard methods?

Hi!
No!
Running in is not that critical...it's just running the engine a little rich and at the same time reach running temperature fast. Simple as that! Please don't complicate things that don't have to be complicated.

The engine is all different temperatures on different parts when running. When the engine stops, heat tends to migrate to even it up all over.

The temperature could be s different at different rpm's, mixtures, & props.

On a Model engine the temperature gage can only be used for comparison purposes and even that would be in the way of bench mark readings at the same place on the engine every time.

The only application I could see this being use on is a turbine where exhaust temps play an important part of ruining the engine. As far as a two stroke you would have to set up your engine and purposely run it lean, overheat it until it quits and record the temperature. Over heating happens and the engines quit because of it but most of the time no damage is done, retune and move on.