Honestly I don't care about ship balance. I'm terrible at PvP but I've played this game for almost a decade, long enough to know that ship stats have very little to do with a ship's combat potential. Ships will always be as good or as bad as the pilots who fly them and stats don't really mean so much.
The Pirate transport is good, sure, but if it's so good then why are people flying Bombers and Gunboats instead? They're doing it because you make more money by charging taxes than you do from pirating cargo. You don't make money as a cargo pirate unless you have a neutral trader to haul the freight for you, which makes the pirate transport useless since it shouldn't be docking on lawful bases anyway.
The pirate transport will always be a useless ship regardless of it's stats. Developers need to add more sell points for unlawful groups so that pirates can actually trade beyond smuggling a handful of commodities.
The question of ship balance shouldn't be about stats. It should be about whether or not this ship does what it was designed to do. The pirate transport is great for killing traders, but it's still useless because most of your commodities aren't worth anything on unlawful bases. If the pirate transport is so good then why are people using Bombers and Gunboats for piracy instead?