Thanks for playing! Your setup sounds really cool.
Auto-stopping is something I have thought about. I am not 100% sure if I have enough space in the pico-8 cart to add this though. I have around 2-3% space left and one or two other fixes that need to go in to a release at some point in the next couple of months. If it's feasible I will add it, but I can't guarantee it.
Sorry I can't give anything more concrete at this time.