Maybe this should be the next Collaborative Game Design project's theme:
Collaboration.
Players are collaborating to make a board game. Each player has a 'secret goal' as to what they want the game to be like when it's done. During the course of thegame players 'argue' over portions of the game (theme, mechanics, etc) by playing cards. As cards get played, or by some other timing method imposed by the game, certain things will become 'set in stone', so eventually the game will be "done." At that point the players look at the finished game and reveal their goal cards. Scores are totalled based on the goal cards, which could have weighted scores for different things.
One goal could be to make the main mechanic a Tile Laying mechanic, so 7 points are awarded if Tile Laying ends up being the Main Mechanic, only 5 if it is a Secondary Mechanic. That goal might not care too much about the theme, but might score 2 points if the game were about Citybuilding.
Another goal might be to try and make a Dealmaking, Citybuilding, VP-Race game (like Settlers), so it would award 3 VP each for Dealmaing as a mechanic, citybuilding as a theme, and VP as the victory condition, irrespective of weather those were Primary or seconday themes/mechanics.
Finally, to add a little spice, the game itself could confer bonuses based on the number of sub-parts it has. So for example, if a game has 1 major mechanic and no secondary mechanics, the bonus would be X. If it has 1 secondary mechanic then the bonus would be Y, where Y > X. If it has more than that the bonus starts to decrease. This bonus would have to be tied into the goals or something so it's not the same for each player.
That was all pretty much off the top of my head. What do you guys think?
- Seth