I agree with you on the role bonuses.
Role bonuses are utilized to help reinforce a “role” for the ship.
All t1 destroyers gain range bonuses for role bonus. This allows them to shoot out farther to counter frigates (combined with the tracking bonuses). Their role is “anti-frigate”
All t1/navy battlecruisers have range bonuses to help apply damage against cruisers at range, the navy variants all have tracking/application bonuses to help them apply to cruisers even better. Making BC’s role “anti-cruiser”.
T1 battleships dont have role bonuses, other navy ships do not have role bonuses. The only navy ships that do are the EWAR frigs, and this is because they have a role of being combat ships with EWAR bonuses (and penalties). Or unique role like the navy maulus with added warp scramble strength (which supplements the existing scram range) and further defines its role. Navy BC’s have role bonuses because theyre Bc’s with an already defined role of “anti-cruiser”.
Navy battleships getting role bonuses wouldnt make sense, as t1 BS also do not have them and navy BS dont have a unique or specific role in mind that would warrant a role bonus.
Pirate ships have role bonuses as theyre designed that way through progression. Pirate is better than navy, navy better than t1. Navy and pirate battleship HP/sensor values arent much different until you factor in the role bonuses for pirate ships, which edge them out past what navy BS are capable of.
Navy ships mainly just need trait changes, slot adjustments and fitting tweaks and then theyll be much more desirable without being OP.