I've got a couple of ideas..I don't know if they're any good, so I'll post them for viewing.
Looking at the Gauss Rail as a kinetic weapon, I keep coming back to something that I think should be part of the TEC on the whole: Armor penetration.
Just looking at GRG (since the rest of that idea is something that can be discussed elsewhere and not derail this thread) it's a big, piercing bullet fired at some insane speed in a place where there is no friction.
Idea 1.) So, if it's fired at something with < 10% shields, it ignores some % of the targets armor, and deals damage accordingly. Have it keep the speed debuff and throw in a small push away from the Kol on anything smaller than a Starbase/Orbital Structure, proportional to it's size (frigate gets pushed farther than a cruiser, which gets pushed farther than a Cap Ship).
Idea 2.) Or, perhaps, have it hit everything in a straight line. Everything. Friend and Foe. It is, after all, a big dumb bullet. Have it slow everything it grazes ("Sir, big bullet just knocked us about, we're getting back on track") Give it a % based on the number of hits, stopping after X (e.g. 100%/50%/10% stop at level 1, 100%, 75%, 50%, 10% stop at level 2 and 100%, 75%, 50%, 25%, 10% stop at level 3) and perhaps have it synergize with FH - Cooldown increase, but no friendlies are hit, add 1 100% hit to the number of targets.
Just a couple of ideas. I have no idea about multiplayer, since I only play with friends and stomp the comp, so I'm making these with no balance considerations.