There are a few cruisers with forward cannons. The Dragon Cruiser has the strongest, I believe. There are also many Gunboats with forward cannons, the Liberty Gunboat among them.
And believe me, I've used many guns of many refire rates. You have more chance of hitting a smaller enemy with 8.33 refire rate than you have with 2.00 refire rate. Projectile speed has a lot to do with it also, but the forward cannon is designed for hitting larger capital ship targets, not smaller ones.
A higher refire rate is not necessary. The forward cannon works fine the way it is now.