What I really wanted were tidal wave or sharkticons turrets mounted on the top and bottom of the vehicle nose cone. But since I have but one Sharky I wasn't gonna use him and Tidalwaves turrets were incompatible. I sort of realised then that he's not meant to be like an imperial cruiser in starwars, more along the lines of Millenium Falcon or something. So the idea was scrapped.
As for big guns, you have to remember that Galvatron is obscenely powerful compared to Megatron regardless of how many weapon points. Think of all my Megatron Supremes firepower energy being channeled through only 2 or so points. It'd flatten whatever got in the way!!!