I had this idea for a campaign and I wanted to bounce it off of people. It's still in the works but heres the break down. It would be a connected game between the 4 lines that featured the 4 Horsemen of the Apcocalypse as an overriding theme.
Dark Heresy Horsemen would be Plague. Since disease can be viewed as a corruption of the body it stands to reason that Dark Hersey fits just fine as representing Plague Horsemen.
Rogue Trader would be Famine. This is a long the idea of an internal thrist for knowledge that can not be quinced. Thus pushing people to explore more and more.
Deathwatch is oblivously War.
And finally Black Crusade would be Death.
This is just the basics of what I have but the idea is exciting and I felt like sharing.