This Is A Good Idea And I Like The Deck, But You Can't Have Umori As Companion If Your Commander Isn't An Artifact
I'm willing to be wrong on this, but I believe since Umori says "card in your deck" and your Commander is not in your deck, they are in Exile in the Command Zone, there is no issue with having a non-artifact commander.
Well I was wrong, but also it seems that with official rules (which I finally looked up out of curiosity) a deck can only have 1 companion. So, if you're rule 0-ing the number of companions, may as well also do as you please for which commander to pilot the deck.
"You may have one companion in the Commander variant. Your deck, including your commander, must meet its companion requirement. Although the Commander variant does not use a sideboard, a companion is not counted as one of the deck's 100 cards."