If Kylo has his lightsaber, they could just lop an arm off, it'd self cauterize, Kylo could Force mind-meld away the pain and terror, and they could have him keep following them around on the promise of a shiny new robotic arm with a built in blaster. They might even feed him part of his own arm. Unless they're out there too long, and the other arm has to go too. And then it gets awkward.
Re: Fill pt. 6 - Kylo/Hux - Roughing it. Hux is Not Amused
If Kylo has his lightsaber, they could just lop an arm off, it'd self cauterize, Kylo could Force mind-meld away the pain and terror, and they could have him keep following them around on the promise of a shiny new robotic arm with a built in blaster. They might even feed him part of his own arm. Unless they're out there too long, and the other arm has to go too. And then it gets awkward.