As already noted, Kaiser is a line fighter. It, along with the IJN and SN BB6s, is optimized for line battles, which today occur almost exclusively in Harbor Assault. Those ships should only be taken into GB to show off or get sunk. Kaiser was also one of the best in World at War, but that's no longer relevant.
If you want to take a BB6 into GB, the ideal ships are the ones you already see the most of: Queen Bee and Charge 'n Maim.