asked me to help him with his 40K SPG project, "Colossus" [link] and think of a shell loading system. Initially I was going to draw just that, but I had too much fun designing this, so I ended up with a suggestion for the look of the whole thing.
The two heavy bolter positions are based on the MG position of the real world M7 "Priest" SPG from WW2, and the improvised sandbag spall protection is a send-up to Japanese warships who used the same method to protect their vulnerable unarmoured bridges.
When firing the gun, the crane will be at a 45 degree angle, as depicted here, and the shell loading tray will be stowed in travel position.