Full size smg's added to both sides (even better would be one in .45 and 9mm for extra options)
Intermediate cartridge LMG for insurgents, and full-power cartridge LMG for Security forces
Bring back the Model 10!
Semi-auto shotguns? (At a higher cost)
While I do love the inclusion of some new guns like the G3, there are a few gaps that I've noticed in Sandstorm. I would like to see another machine gun added to both sides, the insurgents already have a 7.62x54R gun (PKM), so why not give them a 7.62x39 (like the RPD or RPK)? The reverse goes for the the Security forces, who have a 5.56 gun, why not add a 7.62x51 gun like an M60E6 or M240B? I think these two guns would add a little bit of diversity to a rather sparse class.
I also think that Sandstorm would benefit from having some more SMG's in the game rather than having only PDW's or carbines. I would also like to see the inclusion of the M1014 shotgun, I think if it did reduced damage and cost extra, it could add a great alternative to the pump guns in the game (maybe added to insurgent advisor)