Hey, could you do this:
Sheldon Brown recommends that a U-lock be placed around the rear wheel, through the triangle instead of through the frame. The idea is that a rim would be very difficult to hacksaw through, since it is under pressure.
When you remove the old rim from you hub, could you first try hacksawing through it, and reporting to us as to the difficulty? That's your homework assignment. Extra credit if you do the sawing with a tire on the wheel.