Other machines support this functionality, so I don’t thinks it’s so hard. Following the thread here
I think it should be doable to rebuild GRBL with the right settings so that the pause button functions as a door safety switch. Then wire a door sensor in parallel with the pause button.
As to why any of this needed when there are curbs and busses nearby… our workplace provides neither the curb nor the bus so they have no liability if you use them wrong. I’m willing to jump through a few hoops if it allows my workplace to provide a big CNC for people to use. We’ll still require training, but have you met people? They don’t follow rules, so it’s better if safety can be automatically enforced.