THIS!! Thanks we really needed something like this!

May I suggest another variation of the bounty program? Recruiting. It's basically the same with the difference that when you create the task the candidates could raise their hands and submit a proposal. Then you could pick a winner and -as the main reason for this- only the winner would invest energy into this task.

Your current system has the flaw that there will be many people who work without reward, even when they have a good end product. Because there is only one winner at the end.