It's not completely out of the realm of sanity. Plenty of 2WD vehicles out there with rear lockers. Take a look at the Toyota Pre-Runner style. Look at all the vehicles used for pre-running races that are strippy 2WD models w/ lockers that scream through the deserts days before the actual race.
As I recall, the Nismo package on the Frontier was offered in 2WD as well as 4WD.