Any competitive marker is suitable for play from any part of the field. The whole idea that a front needs this gun and a back needs that gun is flawed, and probably due to watching a lot of movies like Predator and Saving Private Ryan.
Not trying to be too brutal, but this misconception needs to be lost as quick as possible.
Ahem. On topic...
Back players need to... wait a minute. Forget back players and front players. Everyone should learn to play from everywhere on the field. If someone asks what position you play, learn the skills and disposition to honestly reply "insert- where do you need me?" On good teams, the mids often pass the fronts, the back players are bunkering opponents, and you can never pigeon-hole anyone.
Everything said here of back players could apply to any player on the field. Every player needs to trust every other. If I have a stand-up on the fifty, and my back player has a lie-down two tiers in back of me, I need to shout for him, while I lay enough paint to allow him to bump up to a more advanced bunker. Why not leave him back there? He'll have a better angle from closer to their flag.