Well, this originally started out as a more 'serious' version of the comic pirate ship that I posted a while back, but it ended up looking more like a luxury yacht of some kind.
I'll have it textured in a bit, but this is the base model:
It has a liberty-rogue style bridge section and engines, while the overall shape of the ship ended up like the heavy tanker. Along each side just below deck level are 5 inset alcoves with turret hardpoints, meant to be used for broad-siding an enemy (very limited turret arcs). There's an additional two turret hardpoints on the deck of the ship at the front. Twelve turrets overall, but only two forward, five to each side, and no backward turrets.
It might be a nice pirate-frigate style ship, something with gunboat turrets but a large cargo hold, low shielding, and large size. I'd image this thing at roughly the same size as the liners or rogue cruiser.
here's a textured version, might change some of the textures but I thought it looked pretty good =P
I'd say make it slow... as slow as a liner, if not slower. This thing should not be outmanuvering anything cruiser sized or smaller, to counterbalance the large number of guns. It's got 12 hardpoints - 2 are forward only (on the deck), the other 10 (split 5 on each side) have small firing arcs to the left and right, with maybe 15 degrees up or down. I'd say give it all gunboat turrets, and a cruiser powercore - trying to broadside someone with such small firing arcs would be like trying to shoot with nothing but a liberty cruiser forward gun all the time, so it should have enough power to repeatedly fire heavy gunboat weapons.
Any bombers that get close to this thing would tear it to pieces though... I'd probably give it a transport shield, 100-150k hull, and 3000-3500 cargo space.