I've run a campaign in Dark Heresy and I'm considering the idea of running a game in Black Crusade. The basic idea behind the campaign is that the group were fighting in the Horus Heresy on the loyalist side when the planet they were on was engulfed by the Warp. After a month of fighting, the planet reemerged in the 41st millennium, with the party as the only survivors.
Rather than running a prologue session, I want to talk to the players about their characters and how they escaped the Imperium and ended up in the Screaming Vortex. After all, the Inquisition would be uncomfortable with completely the party's views conflict with current Imperial Creed. They are heretics by obsolescence rather than by rejection. They are outcasts in every sense of the word, sharing kinship with neither the heretics nor the loyalists.
The idea is that they face damnation by gradual steps rather than by actively chasing it. I intend to run the introductory adventure at the back of the Black Crusade book as the starting adventure (which almost seems written for a party like this. But then, I suppose that's the point behind its ambiguity.)
To allay any concerns over the group being prepared for an adventure of this scope, they are. Only one person in the group is not deeply familiar with 40,000 lore, and she was in the Dark Heresy campaign, so has some foundation on the universe. Curiously, she played a Sanctioned Psyker very convincingly.
Any particular thoughts on the campaign? Anything I should watch out for or traps I could fall into that I might not see?