I think the FISD represents equality between the casual trooper, and the accuracy nut.
the best option for balance in the centurion camp is the allowance of a plastic or resin blaster...
because actually to be a screen used replica you'd have to carry one of the following blasters:
a working firearm with added parts - would require a license and permits to troop with. (most likely a fan film set.)
demilled sterling with added parts - still requires some permits and licenses in some locations. not legal in others. steel billet in receiver, plugged magwell. no trigger. no bolt
resin replica as per screen used - solid resin moulded copies of the base gun with parts added. (might have real scope or real counter.)
I think that a fully modded hasbro that has been fully chopped to the point of replicating the blaster should be allowed if
it meets the centurion level of accuracy for measurements, appearance and functionality.
in that case it would be considered a "scratch build"