I was just reading the MANTRA stuff (looks great, nice one) and was reminded of a book I read as a kid (yes it was a long time ago..) 'Split Infinity' by Piers Anthony, some of you have probably read it, but for those who haven't:

The story is set on a world that has a very interesting tournament running, with players of several categories competing in 'The Game' The basis for the competition is a very large number of fairly conventional contests. The specific contest is chosen by players selecting rows and columns (one each) from a grid of possible contests. As they only control one axis of the grid there is some skill in second guessing what your opponent will go for. One grid selection leads to a second more detailed grid and the players select again. Eventually a contest is chosen. I've explained this terribly, go and read the book, it may be possible to adapt this to the hub.