Interesting question. Given you would likely have to modify the truck to accommodate the 5ver, not sure how the lease would be impacted. I think drilling holes and bolting the hitch in the bed and to the frame might create a problem when the lease was up.
But, maybe they can come equipped with everything you need.. then the next concern would be mileage. If you travel a lot, you could exceed any max mileage at end of lease.
Mike