I like the challenge idea mentioned in Cliff’s blog positech.co.uk/cliffsblog/?p=253 but feel that sending your challenge to a specific person or persons is limiting. As I mentioned in my comment to the blog I would prefer the challenge to be submitted for all to see on the game’s hompage.
So to expand on my comment:
My whole idea isn’t new and is based on Armadillo Run’s method.
You would create a challenge maybe specifiying the types of units the opponent can use.
You would be REQUIRED by the game to ensure that the challenge was actually doable.
You could then submit the challenge to all other players to download via the website.
There would be a running highscore of the player who won the challenge in the fastest time and/or cheapest way.
Without seeing exactly how the game works it’s difficult to know how plausible all this is. For example there would have to be a cost per ship/unit and/or a way of tracking mission time.
Having re-read your post I notice your comment about “open” challenges. DOH! That will teach me to read things properly!