So, Back on topic;
Pete, I strongly support your idea, suggested it myself 2 yrs ago.
Might be an easier task fo ryou to start with a Basic Cargo, though.
As you suggested, sell the AD, I'm sure you'll recoup all costs and a bit more. Judging by the few i've seen for sale, through $200 worth of camping gear in and you can ask $50 000 for it

From a project point of view though, the Cargo simply has less metal to cut. You can buy them cheaper and with the balance, have exactly the storage system you want built to suit the 'new' vehicle.
Probably even cover the cost of the OD setup.