Swords to Plowshares is a great removal for creatures, for example, but a Commander deck with Titania, Protector of Argoth won't be able to use it
Cards like Thespians Stage and Vampire Hexmage allowed you to release the Kraken much earlier than intended, eventually leading to Dark Depths being banned in the Modern format
It feels an awful lot like cheating and, while the character of Karn is great, nobody likes this planeswalker card who isnt playing it
Jodah, Archmage Eternal is a very color-intensive commander to get the most out of his ability, so I highly recommend a consistent manabase over a speedy one
You can also easily go 5-color, which is very fun although most people think that playing 5-color commanders is annoying
It is a recursive beater, it just gets a lot better with extra Assassin support