On more thought I don't see how what you're saying is relevant to my point. The server needs to maintain the current state (which is based on the latest input it has received). No matter how you do the networking rollback or not you can't escape latency causing a problem in perceiving the wrong state on the clients. Thats why with rollback players sometimes see the enemy teleporting. The networking code cannot remove the need for the player to "lead the shot" in some sense.