I find it very hard to believe the unrest is due to lack of police, as if that was the case, you'd need PPV as soon as you had people on the planet. I live in a really small town, about 2000 people, and even we have police. So a single cryostasis chamber load of 10,000 colonists should also require police, if PPV actually is just traditional police.
Another advantage about cheap PDC's is that they are so easy to build and maintain. You can easily get 100 PPV in a single prefab PDC component, which can be built basically instantly by a single construction factory or brigade. In fact, a good cargo ship could probably even carry the minerals you need to assemble it.