I think where it becomes the most dangerous is when a card is creating a huge blast of Treasures that come into play untapped. "I could definitely see a world in the future where we try and make the big blasts of Treasure come in tapped." Most experienced Commander players probably wont be surprised to hear Verheys example of this: Dockside Extortionist , a creature from Commander 2019 that can produce boatloads of Treasure, poetically blasting its own price on the secondary market to more than $60USD at time of writing
Presumed to provide potential glimpses into the future, these Booster Fun treatments were initially celebrated by many players
Putting this all together, we can establish the following facts: A Magic card does not need to feature the traditional Magic card back in order to be tournament-legal, as long as the cards are played in an opaque sleeve
There are no restrictions except, of course, cards on the ban list
Polteageist takes 20 additional damage from Darkness-type attacks
Runic Armasaur in general seems to have a low ceiling into certain decks, holding it back a bit