If the moon really is hollow, maybe those strongly magnetized moon rocks have something to do with its propulsion system. I'm thinking more along the lines of the active drive system magnetized the rocks as a byproduct of its use.
A second thought comes to mind... The moon is 25% the size of the Earth and only 1% of the mass, yet NASA "claims" the moon has 1/6 Earth gravity. Wouldn't that seem to indicate that an artificial gravity system is still active?