What about making a monthly contest for designing a roleplaying game. Every month the winner of the last month chooses two story elements and two game elements and everyone has to choose two of them. At the end of the month the winner of the former month nominates the new winner who has to come up with an idea for the next contest. There is nothing to win, it's just for the fun and the rpgs^^
For example: the winner chooses: "spaceship" and "moral conflict" for story and "d12 only" and "one page" for mechanics and every other player chooses two.
A decides to take Spaceship and moral conflict and makes an battelstar galactica rpg.
B decides to take d12 only and moral conflict and makes a game that sets a fokus on moral decission and uses only d12.
C decides to take one page and spaceship and creates an rules light tactical spaceship tabletop game.
The winner likes C entry the most so he declares him to be the winner. C has now to come up with something interesting for the next contest.
Maybe having to choose three could keep the contest more fokused. What do you think?