It seem really hard to make a cost effective broadside ship compared to one where all weapons face forward.
The following started off as @Veltrdon's ship but I've changed it so much it is basically a different ship now. The goal was to be able to consistently beat Cerberus as @Veltrdon wanted (ship cost limit of 1M), but it still can't really do that.
So maybe someone else can come up with a better design.