Just to keep things fair, we reduce the strength of the Grenade Launching Buss. Either S3 or S4...I honestly would like to see the S6 shooting option filled by the Swivel Cannon, as a champion upgrade for handgunners and handgunners alone (well...maybe Outriders may have a more compact techno version...).
S6, Armor Piercing, Range 36, Move or Fire. It would be perfect for those of us wanting to do pirate-themed armies as well..."Load the swivel cannon matey"