Borrowing some ideas from you guys, here's the first round of mods on my Sherpa.
I built a rear rack out of 1/2" square steel tubing, bent by hand, and attached to the turn signal mounts and the side cover bolt holes. An aluminum plate is attached with sheet metal screws across the two rails. I left the plate plain for now because I intend to mount a box there, just don't know what kind yet, probably a Pelican case:
I'll also be building racks later for side cases. These will probably be a pair of surplus ammo cans I picked up for $15 each. They're actually cases for military night vision glasses and I think they're a good shape/size for this bike.
I had to move the rear turn signals for the top rack, which was OK because I didn't like how much the stock ones stuck out. So I got a set of LED signals and mounted them to the sides of the rear fender. I also installed an extra LED brake light onto the bottom of the license plate that I had leftover from a car project:
In the pics you can also see the new Pirelli Scorpion AT rear tire on the bike.