I've yet to be able to design a broadside ship that I've been happy with. They always seems to end up being not very cost effective. Even against a swarm of small ships, which is where the broadside design should be best I think several smaller ships, positioned back to back or in ring formation if need be, is consistently better.
Anyway, I have a new ship design that I've been experimenting with that seems pretty effective in head on battles,
Experimental Warship: 2,000,000
The side laser arms weren't originally part of the design but they seem to be surprisingly powerful while also making it even harder for an enemy to target the the quad ion cannon banks.
In the end, it has some resemblance to the Cerberus built-in ship even though that wasn't the original idea.