The Chinese are planning to set up manned bases there about ten years from now. I find it hard to believe we will sit back and just let it happen. There are serious implications for national defense if they get a nuclear powered base in operation on the lunar surface. With a powerful enough laser they could control all of cis-lunar space. This type of activity can't go unanswered. We could be forced to go back very shortly.
In that book, settlers from another star system use asteroids as a weapon. Having the high ground and controlling the orbital mechanics of large objects is a fast and dirty way to get your way in much the way you could with your examples.
They could be moved to, and staged in lunar orbit ready to slingshot Earthward. The Moon would provide security for these large masses that in turn would be able to block anything incoming from Earth.
I just speak of this as an example of how cheaply a base on a light gravity world can wreck havoc on a world where getting out of the gravity well is expensive and time consuming.
Humans are ingenious in regards to developing doctrine and new ideas for conducting war, I'm sure people will think of other things they could to to gain power over others. If a new space race develops, it could be ugly and violent of the participants are nose to nose in racing out there, the stakes are that high.