With artillery being a major part of the empire's character, we should have a special character representing this. Maybe just a hero level engineer with a couple of cool upgrades or a weapon only he can use.
This wouldn't be unbalanced in any way and special characters aren't usually used in tourneys meaning that this character would only see the table when it should: in friendly games at home where people try to theme their armies.
I don't play a gun line myself but I think that would be a lot of fun and would provide hobbyists that particularly enjoy the painting aspect an oppurtunity to paint a cool special character.
Ok, throw things now if you want