Well, M40A3 would be good, but only in the hands of MARINE sniper. I guess a good way do it would be to add a new specialist, as said above, a marine sniper equiped with M40A3. This new specialist could replace either mr. Stone, or the lady with SVD.
Back to the missing textures on M4.
Well again they dissapear during the mission, although the everything was ok during kit selecion. However only when used together with SR47.
So as you people said, this must be the case.
But why does it hapen only after some peroid of gameplay. Previously it occured to me in mission no. 4, and now nothing was happening until mission 12. And since that moment no matter what i would do, i cant get those textures back whenever SR47 is in play.