I've sometimes considered whether an external site with DF bounties such as this one would be a good idea.
It's happened for other projects, someone wants something done, people get together and put up some money, a bounty on whatever they want done. Some open source programmer hops to it, it gets done. One example would be
http://www.opensourcexperts.com/bountylist.html , and I'm sure there are many others.
Now our problem occurs when we realize that this is not an open source project, there are what, two or three people at most that can influence the game itself? This limits how far money can go when it comes to influence, because if those few people decide that no, then that's that. Feature X will simply not be implemented for any reasonable bounty.
It would also carry a feel of ransoming donations. 'You can have this $1000 donation, but only if you implement feature X according to this specification'.
Then there would be the issue of trust. What's to say the person responsible for such a site wouldn't simply take the money and split, leaving it up as essentially a scam? What's to be done with the bounties that are never cashed? Returning the donations would be infeasible, so donate to charity? After how long? Does donating to charity make more sense than giving the money to bay12 games anyway, after all they are the reason we even want this feature in the first place? But if the money is given to bay12 games anyway, where did the incentive go?
Anyway, I didn't mean to derail your thread with a more general suggestion, but I think it's a tricky problem overall.