So, it's been a while.
I picked up a Tiger tank model kit a few weeks back, and it has some really nice tracks. I'm feeling inspired to build it into an Orky wagon.
My current Plan A is to build an Orky version of the old M3 Lee tank. I always thought that the lopsided design felt very Orky; the big cannon in a sponson with another turret on top, riveted together. It feels like something slapped together in a rush, which I think is a good mix for Orks conceptually. I'd go with a sponson mounted Kannon (I've got one from the Battlewagon kit going spare), and a little turret on top packing a rocket launcher or big shoota.
The alternative would be to go for something a bit more open aired and multilayered- kind of like a scaled down Battlefortress design. I always loved the exposed gunner pits on that model, with the enclosed roof. Maybe a top deck like the old Forgeworld Gunwagon, but with a big lower deck packing a Kannon in a casemate or sponson.