Elf typal is off the table, since as a mono-black commander theres no green in the color identity
The six-sided die directly introduces RNG into the game, which if introduced today, would probably cause much more concern in the player base Double Spells Each color has a common instant or sorcery with a mana value of five across the board thats considered a double spell. They each do something when they're cast as well as at the start of the next game, a nice 4th wall-breaking mechanic that can lead one player to having a much worse time next game
In fact, it might be a good idea to just change Magic: The Gathering to Bottle Gnomes: The Gathering
On the flipside, taking a Fatal Push to clear a path for Deaths Shadow is sketchy because there are so many more cards that kill it
Secret Lair Drops If you just want a little Whovian splash, there are a pair of sinister drops in the Secret Lair Spookdrop
In Standard, Aftermath Analyst decks are losing the New Capenna lands is Iridescent Vinelasher good enough to make those decks viable in Pioneer