I was looking over the stuff in shield of humanity and one of the options they mentioned as a defect was warp delayed, I ended up getting an idea for an entire campaign out of it. Essentially it would start off with a ship lost in the warp for about 3000 years, the crews were kept in cryo tubes and the gellar fields held...mostly. However the crew of the ship is dead or crazed, emerging from the warp the ship ends up crash landing on planet, aside from a ton of damage the cryo frozen soldiers awaken, gather their equipment and now need to make contact with the imperium. However the world they landed on, well the imperium lost that battle years ago.

I need to decide what is currently holding the planet, as well as the shape the game should take long term, ideas on this front as well as comments on it would be welcome.

For the style of the crash landed ship and the crazy crew you might take a look at the Movie "Pandorum" where the degenerated crew opens these cryo-pods on occasion to get some new "cattle" and everyone things they are still lost in space until they discover they have already landed and after clearing and securing the ship where they think they have done it, they will get this big WTF moment when they realize they crash landed on a now hostile world. (Windows are quite rare on a ship and maybe they landed in some sort of ocean or lake, explaining why their ship has not been looted or destroyed by the victorious force that holds that world.

Maybe they have to take some escape pods and the very little of gear that fits in to establish a bridge head on the near shore and then start to defend them self. Maybe the enemy only attacks in small force because he is surprised by this new threat and they have to consolidate their troops that are maybe some mix of several thinned out regiments that were aboard that huge carrier. (That would allow different regiments for your PCs too) and they have to work together, making use of everyone's special training? Like some light regiments that offers some scouts, some grenadier regiment that brings firepower etc.)

Their goal would be to locate and then secure old and abandoned imperial strongholds (They have still the maps of the 3000y old battlefield) in the hope of locating some long range vox that might get through to some bypassing ships (like Rogue Traders) or observation station. (Though that might take years). Their other goal would be to somehow establish an area where they can live, like a camp in the mountains etc. though these all have drawbacks. If they set up in the mountains they have an easier job to defend their camp, though they have to leave so gather resources like food. Where else they could have their own Xeno-Cattle or Groin if they build up on the plain, though they are open for attacks here.

In the end they are stranded and help is extremely unlikely to happen. Their resources are limited and in the long run there are just two options. Stay hidden and hope they will never find you, or desperately push forward and hope the majority of their fighting force is not on planet. (This would be fun against some Tau colonies that maybe have some humans integrated in their society, that are descendants of some of the loosing regiments that surrendered.)

I like many of FieserMoep's ideas, especially having different regiment types (from vastly differing backgrounds?) for this campaign. I would love to see how it turns out in the War Stories section. I wouldn't use Dark Eldar or Chaos as Chaos are far too dangerous for a starting campaign IMO, and Dark Eldar don't really colonise planets for 3000 years. I would either use Severan Dominate or other generic human seccesionists but not heretics for the confusion factor that might come with the regiments believing them to be IG and introducing themselves as fellow soldiers of the almighty Imperium, only to get open-fired on by their supposed 'allies.' Or you could use Orks for the shock factor the savage Xenos would have on an inexperienced regiment or the danger they would offer to even experienced regiments with such low equipment.

I have very few ideas for how they would re-establish communication with the Imperium beyond those already suggested which are rather unlikely to succeed given the circumstances. To be honest, my advice would be to have the Imperium launch a counter attack once the PC's have a chance to acclimatize themselves to the situation at hand.

I also like the idea and here are a few things:

- First off, when you experience a time slip in the Warp, it will be a relative thing: for you, the traveler, the journey will take the normal amount of time (days, weeks or months). So you jump in with the ship, emerge three months later (for you) only to realize that you were away for 3000 years. Time flows differently in the Warp than in realspace.

- I would make a minor xeno race for the campaign to serve as the main opposition. They were primitive when the regiment was assigned to purge them, but since then they grew into an advanced civilization. Use Tau stats from DW to represent this race, the basic Fire Warrior is a good challenge to a starting OW PC in my experience.

- You can also introduce a "human resistance", the remains of the Imperial forces that still fight the war. the initial mission of the PCs could be establishing contact with this resistance and helping them to cause some havoc so that the regiment can establish a foothold on the hostile planet. Later on, the resistance can be turned into a secondary opponent as they had fallen to Chaos in a desperate attempt to gain the upper hand over the xenos some time before the regiment arrived .

- Extra points if the Warp continues to puke random forces onto the planet, like Ork Waaaghs, Chaos raiding fleets and other Imperial armies, all lost in the Warp for thousands of years.

I also like the idea and here are a few things:

- First off, when you experience a time slip in the Warp, it will be a relative thing: for you, the traveler, the journey will take the normal amount of time (days, weeks or months). So you jump in with the ship, emerge three months later (for you) only to realize that you were away for 3000 years. Time flows differently in the Warp than in realspace.

There are no laws of nature in the warp. As you said, it is a relative thing. You could be traveling 3 months and pass 3000 years, but you could also travel 300 years on a 3 month journey and 3000 years pass. Also you could spend 3000 years in the warp and leave it after 3 months real time.

The thing with the 3 months and 3000 years scenario is just the most popular because it allowed the main cast to stay alive in the scenarios where it was used.

Another brief note I just thought of:

You mentioned that the crew went completely insane between the entrance and exit to the warp. But what if there was a guiding force behind their madness that begins to infect the guardsmen? It starts with a few violent fights, just a natural stress release to such a crazy experience. But more and more suffer from it and get more violent, then overnight, almost a quarter of the guard snap at once and go on a rampage. What caused this is down to you. Disease, dark magic or xenos device would be my choice.