The problem with anti bomber guns is then bombers will be useless, they are terrible snub v snub, and only decent vs Gunboats. i like bombers because they force people to fly smaller capital vessels. With 5-6 cougars today, we managed to take down at least 6 capital ships alone with combined firepower. If you don't like nova torpedoes, invest in flak cannons, i find they are best for countering bomber long range strikes.
I don't suggest anti bomber weps, but i do suggest maybe buffing the cap ship hull and reducing the range of novas.