I certainly think the Empire should go the way of the black powder. And that this in itself makes it artillery-dice dodgy.
I'd like to see a pair of smaller cannons drawn by horses (S6, D3 wounds a piece).
I also think, generally speaking:
bow: S3, range 24 inch
Long bow: S3, AP 2, range 24 inch
Crossbow: S4, AP 1, range 30 inch
Pistol: S4, AP 2, range 8 inch
hand gun: S4, AP 2, range 18 inch
Hochland: S5, AP 2, range 24 inch