I was thinking more in terms of altering the:
"Requirements Max Engines" setting in the Vehicles Text file to 8, 9 or 10 for the smaller ships. Has anyone tried this or am I missing the point somehow ?
Just to clarify my previous point, what I mean to say is that if you never progressed beyond Ion Engine I in the whole game, it only seems right that frigates and the smaller ships should be able to move faster in combat than larger ships.