ACOG is great to have. Yes, you lose your periphial vision, but you aren't gona have your sights up at all times, and hopefully your team members are watching your back and their fire sectors so you don't get caught off guard.
The problem is not the saw gunner, its the other players. When a player is shooting, in a firing line or has stopped moving to shoot, YOU and the shooter need to be aware of where and what direction he/she is shooting. If you have to move, do so behind the shooter. If you can't, tell the shooter your crossing their line of fire and wait for them to let you move.
A proud member of
Team SPQR"Non Facete Nobis Calcitrare Vestrum Perinærm"