The best solution would be to buy a cheap set of used 215`s with rims, wash your good tires, put them in plastic garbage bags someplace dark and cool (on the side). Every couple of weeks or monthly, have somebody drive the Jeep around some, until the motor and tranny is up to operating temps. and the fluids have moved around some. Put a stabilizer in with your fuel, after six months, some of the bad stuff starts to settle to the bottom of the tank.
Wash it and wax at least a couple of times a year (waxing the rubber window seals, with black colored wax, has worked for me). Pollen and other stuff that settles on the paint and rubber becomes acidic after a while.
If you can´t get temp. plates or insurance for the bi monthly exercise for the Jeep. The driveway will do, just bring everything up to temp. and move it around as much as possible in the driveway.
A coat of WD-40 a few times a year will really slow down rust, especially in the engine compartment and other rust prone areas. The WD-40 has a little wax mixed in, that is persistant and lasts longer than plain oil or most other spray oils.
Like mentioned before, most of these methods are what we ex military figured out over the years.