I always wonder how these places don't get ripped off left and right by people just making the first payment and bailing with the hardware but i suppose they probably just make up for it from the handful of suckers that actually keep paying for stuff.
I suppose if you could put custom firmware on the card, you could have host-side software that talks to something remote and to the card and has to activate the GPU each session.
I think that the issue here is less the technical barriers and more "the financial side doesn't seem to make a lot of sense".
these types of "rent-a-center" businesses don't exactly target people with credit scores that can be damaged much (it can only go so low), these are the kind of places people who are extremely irresponsible with their money go to get things because they literally have no other option.