Do the guns really need to converge? How many gun types really need convergence? These are questions I leave to you.
Keeping it true to WCII would mean the faster refire rates for multiple guns. You don't have to do it for all the guns, massdrivers and particle guns are the main culprits since they get mounted without another gun to back them up.
You should be able to do it for most gun types, it all depends on which ships mount which types of guns and how far apart.
Please do this, it would stop the Light Fighters from sucking, at least.