There are several industrial/transporter ships that can defend themselves from varying threats in the mod already.
The (various) liners and the Shire (possibly also the Akegata) are recognised as the toughest, with the highest dps output. They take on cargo pirates with room to spare.
The Hegemon is a beast that only suffers due to the four mining turret bonus- reduce your number of mining turrets and you increase your offensive power greatly. It has good agility and the ability to fire a tcd backwards.
The ALG Golem suffers due to the low number of turret hardpoints, but it is very tough and has staying power.
The Mafic is the most defensive/offensive mining ship out there due to dodge capability and the Snac. The ability to mount fighter weapons allows you to defend other mining ships/transports from bombers effectively.
If all else fails, and the pirates keep logging on -in your field-, rename a gunboat/bomber to match your mining ship. Watch them log on. Cue hilarity.
If you want to win battles consistently, use a high level Capital armour.
Edit: The hegemon is actually very good at fighting. I've beaten up Hessian gunboats in it.