Hmm, maybe there's a simple legislative fix for this problem. Basically vendors that want to make you "rent" devices would have to allow termination for convenience at any time by customer including repayment of any fees paid by the customer for the device.

Termination for convenience is a standard term in contracts, hence well-understood by corporate lawyers. The repayment could be reduced using a depreciation schedule so the longer the device is in your hands the less that's returned.

I think this would work. The legal machinery is already there. The market would work out the details.