I didn't like the look of GW's standard Defiler, but I though several Brass Scorpion based off the model were pretty interesting. Anyway, this is my Defiler using 2 Defiler kits and a Fantasy Hell Cannon.
Inventive! I like the blues you have given the armour, but I think the model would be even better balanced if you had bulked out its body behind the cannon (which is an excellent choice, by the way).