I don't think Disenchant and Geth's Verdict should be in mainboard as they can be dead cards against different decks. Geth's Verdict is really only effective against Bogle while Disenchant against Affinity or Enchantress builds. They are still great, just not against every deck. Since the budget doesn't seem to be an issue, you could replace Duress with Thoughtsieze.
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Greater auramancy could work in this build, gives shroud to your enchantments.
A planeswalker cannot be your commander unless stated otherwise on the card
(In case no one noticed, this is clearly NOT a joke)
Honestly, very good deck. A shame that it isn't legal in any format though. I'm surprised this meta hasn't appeared in formats like vintage.
So, a big part of Commander is creatures. While there are some commander decks out there with minimal creatures that work well, it is vital that you can fight on all fronts in commander, as there are going to be players that will fight through the life gain with massive Eldrazi or dragons. While creatures don't have to be the central focus, it may work in your favor to expand your library of creatures. A great option would be vampires, as vampires have that black/white life drain style that this deck most definitely has. A couple of fantastic additions to this deck would be Bloodline keeper, bloodbond vampire, the haunt of hightower, Vona Butcher of Magan, (an expensive but a goodie) Elenda the Dusk Rose, Vampire Nighthawk, and this isn't a creature but Blood Tribute would work VERY well with Sanguine bond.
A couple of things, first, commander decks aren't "technically" allowed to have sideboards but in casual play, no one cares. Another thing, your curve is VERY early for Commander. While you don't want your deck to be too saturated with high cast cards you are definitely gonna want a few. The problem with having too many low-cost cards in Commander is that your hand will dry out quickly because you will liquidate your hand by the end of the 7th turn. While there is some card draw heavy hitters like necropotence and skull clamp, it won't work consistently enough to constantly keep your hand full.