OK - so we have:
1.) Gotta have a table, just because. It can be only one table, that's cool with me but it would need to change daily - or have different tables with different contracts.
2.) I really like the reputation idea, but it would need to tie-in somehow to the game. Maybe it can be guild related? Higher rep for players directly affects your guild, maybe the leaderboard somehow.
3.) The reward base like Loose_Lee brought up is good. It allows you to get rewards as you progress through the board, to an ultimate reward.
4.) The story line is what has me really drawn in. I love the fact that you may interact with a main character to get an assignment and have it tie-in to the board.
5.) Refreshes being limited, time limits are good - makes people have to think fast - sometimes it's good, sometimes you make mistakes - could either win or lose the battle for you. I like this more I think about it.
6.) Ultimate goal would need to be big, no doubt about it. No shards at all - full characters and if you already have that toon, you can trade it in at the shard shop or whatever.
7.) The black market idea still has me going. A way to sell back or trade in what you've earned to get something better and better.
I like the fact that it will make players think outside of the box a little and force them to do things that may cause rep to increase - or fall depending on the decisions they make.