Being hard to remove is great, but another way to ensure that having your Commander removed doesnt set you back (or to put people off removing it in the first place) is to make it low EV for them to do so
You can also use Pestermite or Zealous Conscripts for your untapping
Cards with multiple card types are at a premium, so the deck is full of stuff like: Solemn SimulacrumSolemn Simulacrum Dryad ArborDryad Arbor Demonic CovenantDemonic Covenant Theres plenty of self-mill to fill your graveyard: Deadbridge ChantDeadbridge Chant Nyx WeaverNyx Weaver Crawling SensationCrawling Sensation You also have a couple ways to get those cards back, like ReanimateReanimate and Whip of ErebosWhip of Erebos
Junji, the Midnight Sky Our penultimate Dragon Spirit in the cycle inspired by the first slate of cards like Kokusho, the Evening Star
From the famous names of MTG like Ajani to warriors in the Universes Beyond like Marneus Calgar, all of these generals can be great leaders of your next Commander build
Consider how useful every card in your hand is, because there's a chance you might play all of them