Good evening, I've decided to make these more public now that I've had time to test them on my human guinea pigs and knocked a couple of rough edges off them.
The Open System
https://docs.google.com/file/d/0B-UM1Pcqre48NG9oR1daT2RuU0k/edit?usp=sharing
This is designed to mate-up characters from Rogue Trader, Dark Heresy and to some degree also Deathwatch, into the Only War system. Yes, it is very basic and pretty much all crunch- I don't want to tread on anyones toes so to speak as far as intellectual property goes, I just like free-form games where people can play and build what they want.
Of course- with the GM's approval, quite a lot of that is needed
Theoretically, you could also put the Only War character in there as well, however they would need to be 'built' with this system and quite a bit of jiggering to match up with the other characters and some addition or removal of the Regiment rules, skills, talents, gear and aptitudes.
Rogue Trader characters are also technically in there, as are more advanced types of classes like Sisters, Navigators and of course, the Scout Marine. I'm not going to inflict a full Marine on a starting party ...no, they grow their implants over time until they're real marines and hopefully the rest of the party has their own xp under their belt. The use of marines should be carefully monitored by the GM, however I have used them in games and it does seem to work fairly well.
If you wanted a Rogue Trader, the Imperial Officer template is there, you'd have to do a bit of ship and influence engineering though via the RT books, like I said, I'm not re-printing vast swathes of material that isn't mine. The only one who missed out was the Void Master as it could be built off any of the others really, but that's sort of the whole point, you start with a career and build it around where the campaign takes you.
Have a look, any particually hideous problems let me know in detail and I'll consider ammending them. But, its an open system, tweak, re-work, add and jigger about as you see fit to suit your games and group. (I just started the ball rolling so to speak for you)