I don't know if its any good but no harm running it past you so...
Interceptor class - Lightly Armed Though i would suggest it to have its own specialised weapon. Due to how i suggest such a ship would operate.. Lightly Shielded (Class 8 LF shield)
Running speed without thruster 199 i will explain this later... I would think of the models as a small LF ship (patriot for example) With VHF amount of engines. Plus some ominous looking thing (that looks like an engine.)
This would in fact be the thruster. Now heres where the "Balancing" comes in. the ship will have 4 minutes where it can move at just over cruise. That with the thruster. So this speed cant be exploited make it do what traders do and slow to its normal speed quickly. (1-2 secs). However the thruster power does not regenerate (i believe this is possible.)
The Purpose of this ship would be to intercept enemy vessels (such as bombers) at the outskirts of the territory of said faction. It would also serve as a smuggler catcher. As well as foiling terrorist plots. The speed it achieves is from a liquid fueled rocket booster (or something more futuristic.) It has smaller standard engines for conventional flight.
Now back onto the weapons... because of this ships special usage would it be possible to have a locked special weapon fitted which had a very high speed and rapid firing. As to disable hostiles from long distances without the need for cruise disruption technology.
I would have the turn rate of this ship quite low. As it is basically some ship that just chases after vessels. Plus with all that mass from the engines the turning would be hampered enormously.
As i say just rough ideas plus most of what i have said before has been shot down by simple flaws in what can be coded. So it will definitely need a fresh pair of eyes..