The force at the attachment point is constantly changing and depends on several factors.

- the weight of either airplane.

- the performance of the engine on that particular day (varies by altitude / airspeed / temp / mixture / type of fuel / ...)

- the instantaneous weather conditions

- the performance characteristics of either plane.

- slack in the rope (no tension to two times the weight of the glider)

- the glider's towing position (below / above wake)

- crosswinds

- the glider's preferred towing position (depends on visibility from the cockpit, e.g. if someone has a phone or a tablet on the dash, the towing position will be different)

So it isn't really a trivial problem, especially when false positive or false negative will lead to a crash.

Oh btw, it needs to be able to react in milliseconds (so no AI, unfortunately). Here's an example of what an early release looks like btw: https://youtu.be/Gu0mZC2mLEg?si=dzVMxG-rW5624T_m

notice how he's always on the stick. Also notice how fast it goes from stable to unstable positions.

> even a crash

Recklessness is never the answer in aviation (or coding matter of fact). Practically, good luck convincing insurance to cover a 100 ton (any appreciable cargo load) plane that might fall out of the sky on any property in the general vicinity.