Whether or not they've ever read a Sgt. Rock comic, the people who'll go to see a space war movie (SF fans, for the most part, unless it breaks really big, which I wouldn't expect it to), are the same people who are hyper-nitpicky about source material (not that you have to be hyper-nitpicky to see the problems with this). That's what I mean about alienating the potential audience -- not the Sgt. Rock fans, but the legions of anal-retentive SF fans who'll cry foul given any opportunity. And this here's a good one.
If this thing ever gets made -- which I doubt -- it'll tank.