The Riot Shield is a huge advantage to Assaults compared to other classes in terms of back protection.
It simply reduces the amount of shootable areas to a tiny portion of the top of the head, the legs, and some of the arms. The only way to shoot these people when they're prone tends to be running towards their legs and shooting them or proning and shooting them in the head. The shield needs to be made slightly smaller when undeployed.
Something like this, for example, where the sides and top pop out as well.
Otherwise, it literally is portable cover, especially when an assault gets killed and their shield simply becomes a shield on the ground that deflects all bullets fired in a prone position.








