So, a new version of Final Liberation?
Course, there are some differences - since it was based off the Epic rather than regular tabletop, its much larger scale battles. And the reinforcements bit is much more like classic x-com than perma-death from a fixed pool.
In the end, sounds like you're looking for a combo of DoW2 (the single-player part) and Final Liberation. Final Liberation for the overall campaign map, and combat more similar to the DoW2 campaigns, just with the ability to lose guys instead of having them go down until revived. (Though, to be perfectly fair, I'd like some limited means of reviving or repair, like the revival chance in Enemy Unknown. Just so one unlucky shot doesn't foul up your whole campaign. Even Terminators can go down fairly easily when matched versus a lot of scary stuff). If any game companies do create something like this? SHUT UP AND TAKE MY MONEY!!!
Stepping back a bit, though, there is hope for stuff sorta like this among 40k video games. There's the in-production Space Hulk game
which could easily pan out as a smaller-scale x-com esque 40k game, and while I admittedly haven't played any of their stuff, the fact that Slitherine
now has a 40k license and apparently does a lot of turn-based strategy games gives some hope as well. Though, Slitherine? I don't know much about you guys, but don't screw up the license.