currently the balance is 32 positive cards and 32 negative ones, where the positive and negative are based on whether I feel the card will advance the board state or stall it.

This is a way to play magic I recall from a while back that influenced the official planechase variant. What rules i didn't remember I created, but the experience should be very similar. Here's the plan: These cards will be in a facedown deck in the command zone and there will only be one face up at any time. The face up one (the 'active' one) will be "owned' by the active player and its effects will operate normally with the exception that it cannot be removed or targetted in any way. The first three rounds proceed as normal, but right before the starting player's 4th turn the first card is flipped from the facedown deck and will be active by that player's untap step. When one of these cards is flipped over a d4 die will be rolled, and that card will stay in play for the rolled amount of rounds, after which a new card will be revealed and the process repeated. The game can end in any normal manner.