I really like it pretty much as-is. The middle engine on the back annoys me a little bit... Maybe attach it directly to the back of the ship, with the other two engines sticking out like they are now?
If it's going to be larger, I hope it retains it's agility. It's the one thing that made the Rogue Gunboat a great ship to fly. Maybe add another turret mount on the bottom of the ship (for a total of 7) and up the armor a little bit (not too much) to compensate for the fact that it's easier to hit. I could see this ship with a gunboat forward cannon, but I remember hearing somewhere that Igiss didn't want them on new ships.