The Ancient Kamados used a plug to regulate the intake. If yours does not have one, I would get a stainless steel draft door from Big Green Egg, drill 4 holes and mount it.
I have a couple Ancients, and one of the biggest problems with the plug dampers was when people shut them down after cooking the expansion and contraction caused the pot bases to crack when the plug was inserted-hence the the invention of the slider (so says Richard Johnson in old Kamado.com forum posts)
Sounds like you have a plan, I'd repaint the bands-but better yet, replace them with BGE spring assist hinge bands (you will be happy you did!) Personally I wouldn't mount a thermo in the lid, use a remote probe on the grate instead. The cart looks to have been modified, which makes it look more stable, but don't push when you move it-they have a tendency to flip easily!
Get a BGE DFMT (dual function metal top) for the lid.
As far as painting-I have had good luck and also bad luck repainting some of mine. The bad luck I've had was repainting a Medium Ancient similar to yours. Mine was in baaaad shape, but felt I did a decent job restoring it, but even taking the extra time to prep the surface, the pain has not adhered and has flaked off and it has not even been cooked on. But on the other hand my Modern Imperial Kamados are in great shape. Others have repainted theirs and had success.
Check out the Naked Whiz FAQ's and the Imperial Kamado website for more info. If you have hours to spend trolling through the Kamado.com forum archives, you might pic up a bit of info, but its more like a duck hunt at a swimming pool!
I would keep it as original as possible if it is in as good of condition as you say, but it will never be as versatile as a new ceramic Kamado ie. BGE or Primo.
Good luck and welcome to the Kamado Rescue Unit!
Brian - Left Hand Smoke BBQ PNWBA 2010 Team of the Year
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