I don't think using the two cannons would be awful. If I were to do this, here's what I would do. It should work, I think ...
1. Import both cannons in the same exact position. Name them Cannon_1 and Cannon_2.
2. Make everything but the wheels visible on Cannon_1. Make the just the wheels visible on Cannon_2.
3. Import a ball prop, and position it along the axle of the wheel's.
4. Parent the ball prop to Cannon_1.
5. Parent Cannon_2 to the ball prop. You will end up with a hierarchy like this.
Cannon_1 > ball prop > Cannon_2
6. Use Cannon_1 to move the cannon around or whatever you want to do with it, and use the ball prop to rotate the wheels.