I really like the idea of the shelf bracket on the side of your drum. A thought to your water pan being a pain to get out what I did was I took a 22.5 weber grill turned the pan upside marked it and cut the grill so the pan rim sits on the rack flush with the pan portion below the grill. For you this might help so you can shorten your self supports that stick out as the shelf brackets will hold the grill not your water pan.
Works well for the pan and difuser can sit on top if you choose.
But I like Bud-Man's may look at trying this as well on mine.
Lot of great ideas from everyone