Hmm... But Planes are already a card type, as is called out in the Gatherer ruling on Fertile Imagination, so you'd need a new name for this.

I think the idea of this (as discussed over at Plane: the card type) was that amuseum is errataing Planechase out of existence :)

Right, these Planes cards can be put in normal decks , not just when you're playing Planechase. Instead of catering to a tiny niche of players, let's make the unique flavor of the game a part of normal games.

as for fertile imagination, can you even put official Plane cards in your hand? for that matter, other cards that stay in the command zone would not affect fertile imagination at all. actually is it appropriate to name card types that aren't legal in that particular format?