I thought that we should throw up a thread for discussion of possible campaign ideas that can be used or perhaps played in some point in the future, and perhaps give some inspiration. This is just kind of my basic idea.
Traitors or Heretics: The players plays PDF forces on a standard civilized world which is abandoned by the Imperium to an Orkish invasion for the sake of preserving troops against a Tyranid Splinter Fleet and everyone expects the world to fall, but through a heroic defense the PDF manages to hold the line and defeat the Orks despite all odds.
But as soon after the victory an Imperial force arrives to collect all able men and strip the world of as much resources as possible to help against the Splinter Fleet. Enraged the world rises against the Imperials and drive back the forager force and overwhelms the local Imperial institutions and proclaim their succession.
Seeing weakness a Chaos cult stages and uprising to take control over the planet but are also defeated after savage fighting where the local mutant population is purged, and the same fate also comes to a pro-Imperial insurregency which tries to revert power back to the Imperial powers before the Imperials arrive.
After a few years of downtime the Imperials do return intent on reclaiming the world and a savage war is waged in a world war 2 Eastern Front style brutality as the Imperials slowly overwhelms and purges the planet of traitors. In the end after heavy fighting the separatists stands at the edge of defeat and grasping afte straws. This is where they are approached by both a Chaos cultists who promises them that he can arrange for the tens of thousand of people still alive to get to a ship in orbit if they help him conduct a ritual. And at the same time an Imperial preacher apporaches and says that due to the fact that the separatists have not let their faith be corrupted despite the treachery they may be given a chance to earn the Emperor's forgiveness in a Penal Legion for the soldiers and in a new colonization attempt for the civilians.
Hence the players can take three choices; either go with the cultists and be transported through the warp onto a Rogue Trader vessel that they will need to overwhelm and capture or subject and sweet-talk the free-spirited Rogue Trader into accepting them OR they can accept the Imperial proposition and join a Penal Legion and so return to the Imperium OR they can have a final battle in a grand last stand scenario.