I want a 40k co-op game that is essentially DoW 2's campaign.....except that it's fun.
Seriously, the maps were so boring and the engagements were too. Send your FC in on a charge, have Avitus set up with a Heavy Bolter or Plasma Cannon. The tact, assault and scout squad are basically secondary units to that equation.
Space Marine got pretty close to it in a 3rd person perspective. Better level design and meta-game ideas would have made that title a real winner in my book. It shows off the 40k IP very well, but it gets a little mindless once you sort out how the combat mechanics really work.
So for me it's not that they need to make an entirely new game. It's just that no one, not even DoW 1 really, has completely nailed the mechanics with which you act out your 40k fantasy. There's always this....layer of gameiness getting in the way, is the closest thing I can articulate. The whole planetary assault setup of the DoW 2 campaigns really demonstrates what I'm talking about, as do many of the side missions. When those things are included and they're not done to the hilt, they become a liability. Especially in a game like 40k that cries to crap epic everywhere it goes. Suppressing the invasion fleet on Meridian isn't epic, it's a goddamn chore.
With DoW 1, it was always clear you're playing in a very generic RTS setup, although I don't really hold that against the game (as it pioneered a better version of territory-based gameplay and that was huge.)
In DoW 2, the campaign missions feel like a chore rather than a mission, you've got to do all these things to get the highest score or you don't get as much XP, and it leads to kind of a mindless experience of 40k whackamole. And even "playing your way" can be unexciting: running across an empty map several times, picking off guys one at a time because the AI isn't all that smart or the godawful boss fights that really were intended for co-op.
In 40K: Space Marine you're just on rails the whole time, and the quality of said rails can vary a lot. The combat mechanics, while promoting a lot of smashing and bashing, aren't very deep or well-balanced. The execution self-heal thing is actually a liability later on in game. Surprisingly, I found MP 40K: Space Marine a way better product than the main game. And I'm far more likely to pay attention to SP campaigns before MP. But the MP in that actually started to make me feel like "40k! Fuck yeah!"
If you're going to make the game about 4 space marines slaughtering EVERYTHING in their path, don't make a level with a finite amount of enemies scattered around in groups of 6 that you have to hunt down. If you're going to do a FPS in the darkest of millenniums, take advantage of that and script some real action and a real sense of the world! Instead of the rail road tracks 40K Space Marine found itself on, with the excuse the planet was fucked as a reason to keep where you are and what's going on fairly staid and repetitive.
That probably sounds a lot like gamer whine, but it is what it is. I think what's always lacking in almost all of the game is some level of detail to things: your characters, the scenario or your options (Atmosphere they all generally nail.) DoW 2 campaign and 40k: Space Marine MP have lots of great meta-gameplay details (character driven advancement), and it's stuff like that which needs to be happening more often.
I'd give most 40k games by Relic an 80% or slightly better. So I'm not complaining a ton (other than the initial shock at what DoW 2 turned into.) As games though there's still something missing from the experience that they, and I guess I, haven't quite figured out. DoW 1 felt like it had a maturity in the design and vision for the game and what it really lacked was time to add more things or the tech to make it amazing. (And then they backed away from the most interesting tech created in CoH for something much less interesting in DoW 2.) All the games from DoW1 have felt like whoever has the grand design ideas isn't quite as...mature? I guess, and enjoys putting things in little boxes and then shutting the lid on the idea and calling it good.