I just had this idea come to me a few minutes ago. What if ships were able to fire their non-guided weapons over allied ships based on their relative size in a manner similar to guided missile pass-over.
For example, a capital ship can fire over allied cruisers, destroyers and frigates as it's larger and other ships are moving up and down more relative to it (imagine the 2D gameplay representing a 3D space battle). A cruiser can shoot over destroyers and frigates for the same reason, destroyers can shoot over frigates and frigates can shoot over destroyers as they are small and nimble and only longer range frigates will be able to use this effectively. Since cruisers and caps are significantly larger they would present too large an obstruction for frigates to shoot over.
Guided weapons would keep their pass-through-until-fizzle and projectiles could revert to their normal behavior (ie being able to damage friendly ships) after reaching max range (or not). Torpedos could keep their friendly fire for balance.
I think this would help alleviate the cramped 'grindy' feeling of the battlespace in large fleet combat as both fleets rub up against each other to try and pick holes in each other's lines, rushing to punish ships that dare to overextend while smaller ships do little except get chewed up by overwhelming firepower and become obstacles to larger ships applying their firepower for risk of friendly fire, basically being usurped by the far more replaceable fighters.
It would allow capital ships to be screened by cruisers, cruisers by destroyers and destroyers by frigates, and allow frigates to more effectively work as longer range destroyer support using a destroyer as cover, all without hindering the larger ship's maneuvering and firepower. It would mean that ships smaller than the average in any given engagement have more utility as they are not relegated to flanking and escort duties to keep them out of the way of bigger guns.
I know this is a bit of a wordy explanation, so thanks for staying with me. I haven't thought this idea through completely and I have no idea how much work it would take to implement, but I'd like to know what people's thoughts are on a mechanic like this. Could it add depth to fleet engagements or is it unnecessary/unbalanced?