Dice Hate Me
The boardgame blog with worse luck than you! dicehateme.com
We add in the red die to be rolled with the normal three dice under the following rules:
Red die comes up '1' you have to discard a card at the end of your turn, after you would refill your hand (if eligible).
Red die comes up '6' you get to 'tap' a ride. A ride that is tapped stays tapped until either: someone untaps it with a 6 on the red die, or the person that originally tapped it picks up the red die again (one full round). While a ride is tapped, it is considered to be out of play and cannot be manipulated except by the red die. A player can tap his own ride for protection, or another player's ride to prevent building on/completing.
This definitely adds another layer of strategy to a game rooted greatly in luck.
Sounds like a couple of fun house rules to me. We'll have to give that a try!