I think people get the idea of a tier system and a role system mixed up.
There are current imbalances in the ship role system, where multirole ships outperform dedicated role ships in many cases because of their number of internal slots and ample power. A balanced system would be one in which a combat role ship, set up for combat, will outperform a multirole ship set up for combat. Unfortunately, that's not the current situation.
There are also imbalances in the weapon role system, where ships have been given disproportionately high maneuverability to accommodate the lack of focus on specific jobs for each weapon/mount type, and a general rebalance of the hardpoint system. This makes any sort of tier-to-tier balancing almost impossible.
It's really a two step process. You balance weapons and give different weapon types a role. Lasers are/remain effective against shields, not so much against hull. Make them less effective against internal subsystems as well. Multicannons should have limited armor penetration but a high hit rate, making them most useful against fast, lightly armored targets. Cannons have a lower hit rate, medium penetration, and high hull damage. Railguns/PAs have very high penetration and moderate hull damage, with very high subsystem damage. Missiles/mines deal high hull damage with moderate penetration, low subsystem damage, but they deal splash damage allowing them to deal damage to subsystems with a near miss.
Further in step one, you maintain the current fixed/gimbal system, while increasing the damage of turrets to match gimbals, but do not allow any targeting of subsystems with turreted weapons. Turrets, however, are changed to track slower based on weapon size, meaning only a small reduction will be seen when using a small turret, but a large reduction will be seen when using a large or huge turret. This means that your weapon type and size both make a difference in what targets you're best suited to engage. A Vulture using dual gimballed multicannons would be very effective against a small fighter, but would have very little chance engaging large targets. A Railgun setup on the same Vulture would be very effective in a limited engagement with larger ships.
Beyond that, you increase ammo counts based on comparative hardpoint/weapon sizes, meaning that a small multicannon turret in a Large hardpoint might have 3x the normal amount of ammunition, making undersizing weapons attractive in prolonged combat, especially when you want to set up to be more effective against smaller targets.
Once that is complete, you can start looking at ship tiers and how different ship sizes should interact. Large ships give you the most options, the ability to build effective all-rounders, and the tools to get you out of a fight that isn't going well. Small ships require more specialization and lack staying power in both shields/hull and ammunition counts. This allows for a general reduction in ship maneuverability based on ship size, combined with an armor increase inversely proportional to that change. This gives larger ships more ability to stay in a fight longer both in survivability and offensive power, but makes them less able to directly counter small ships without either escort craft or specifically equipping a number of small hardpoint turrets.
The next step then becomes easier. Now combat-specific ships can have armor values, maneuverability, or hardpoint availability increased to suit their role, while trading ships have seen a general survivability increase and can be set up with additional cargo bay slots in a balancing pass.
The problem with simply "nerfing the python" is that it doesn't address the core issue which is a lack of clear vision regarding the intended roles for each ship, and some plan towards making sure that the cost of a ship isn't the only factor in determining its use.
