What if there were an option to tie the server speed limit to the mass of the ship being used? Fighters SHOULD be faster than cruisers after all.
Not to gang up on you, but from a purely balance standpoint having 1 always faster then another doesn't seam very wise. Anyone who has played a game were one person can run twice as fast as you knows how it feels to be a immobile object in a world filled with race cars.
When your the slowest thing between the stars you might as well be a space station or a blimp, if everyone else can run laps around you and your so slow you can't hit them.
What a larger, bulkier vessel should have less of is Agility, not speed. A giant ship should have a harder time turning on a dime(Read as: Needs more thrust) and you should 'out run them' not by running in a strait line, but running in a serpentine path so they have to constantly keep turning to try and catch you, letting you get away.
Note I am not a physicist, nor a master of mathematics.
just my opinion, take it with a grain of salt.