I’m preparing for my Negotiations class, and I had an interesting idea for a Chess variant in which each move must be negotiated by the players. The player whose turn it is proposes a move, and the players bargain until they agree on the current player’s move. If the players cannot agree within 5 minutes, each player loses one piece of their own choice.
The negotiation dynamics would be interesting. On the scale of a single turn, you could only come to agreement if the players found a move that they each thought improved their position. However, it would also be possible to negotiate for concessions over time — “I’ll give ground here, but you need to reciprocate on my turn”. There could also be situations where one player has an incentive to run out the clock because she feels that the other player can less afford to lose a piece.
I think the endgame would be a problem; as the tactical situation became simpler, it would be harder to find perceived win-wins, and the downside of not honoring long-term agreements is reduced. No one would ever agree to allow an opponent to move out of check. (I suppose you could have a rule that moving out of check is always permissible, even without an agreement.)