Seems really interesting and paranoid's concept is neat.
Now I know that being underage I'm not myself nothing more than a chairsofter, but I think that such game should not aim for the more players possible BUT for experienced and motivated players, else it would be boring with people complaining, getting demotivated, etc.
I've recently seen a video of a France-Belgium game held over ~48 hours with NPC playing residents of the area that could attack both sides with "rocks" (made of foam) just to disturb them but could even 'kill' them. This makes a much more realistic experience, in my opinion.
Also, what Brian suggested with the "Hold your lines, you have a safe zone and supplies. Don't hold them, you don't..." That's something hard to setup as it everyone would need a radio so they know if the safe zone isn't safe anymore but that would rock.
And complete teams separation:
Recce/Specops and sharpshooters could act in small teams and go behind ennemy lines (but then the safe zone thing would be screwed...) to observe and report or destroy assets...
I won't explane much as I'm sure you all got the point of making a real milsim instead of just a big skirmish.