Here's the thing: I don't normally do groups, and I'm clueless when it comes to systems and suchlike. However, I have this idea that really - at least in my own opinion, which I respect - lends itself to a group of four. Or three, but preferably not five. For the sake of avoiding confusion. What I have in mind will in some respects be similar to Space Hulk, and to some extent the video game, Dawn of War 2 ( not so much the first Dawn of War ).
The basic idea is for a squad of three or four Space Marines to be deployed to some godforsaken hellhole. I mentioned Space Hulk, and that is one possible option - having it set on a space hulk. However, as compelling as that setting is, that's far from the only option. It could be a Chaos-infested forge world, or a backwater overrun by Orks. Basically, the players take the role of the Space Marines, and kick alien ass, while at the same time having an actual story with actual depth, to add to the action.
The squad itself is flexible. I was thinking something along the lines of having one Sergeant, a Tactical Marine, a Devastator, and some fourth option ... Assault Marine? Apothecary? Librarian? Techmarine? Dreadnought, even? Chapter they belong to is flexible as well, though I lean toward something basic, something that won't require everyone to do a lot of reading. As interesting as I find Space Wolves, I know nothing about them!
What I'm interested in, is for them to be more than mere one-liner-spouting, faceless super-soldiers. I'm interested in distinct personalities, strengths and weaknesses. Space Marines are still individuals, after all.
Like I mentioned in the first paragraph, groups aren't normally my thing, and I'm nervous about starting something. That said, if there's genuine interest, and people are willing to lend a hand in making it happen and making it work, I'd be more than happy to do my part. So here's just throwing the idea out there, and seeing what happens.