I was thinking about this a while ago but more based around owning shares in the ‘fund’, which would then earn profits which would either go directly to the shares or (in your case) be invested in @ocdb.

In this idea I would recommend that everyone would have a certain amount of Steem at stake for if their bets didn’t turn out well. The incentive system here (I believe if I understand this right) means that the participants can only win (from correct predictions) but the organizers always lose if users make incorrect predictions.

But other than that I think this is a great idea!