If you want to do this, what I would do is start working on a list of needed improvements. Post them here and let people comment on whether they're important, poorly thought out, or whatever. Then start gathering contributions towards a bounty fund. Put a bounty on each improvement that gets some agreement and document what has to be done to claim them. (Is submitting a patch sufficient? Is a pull request? Must it be accepted into the client?) Then perhaps break the larger tasks into sub-tasks and put on intermediate bounties.
It was an offer of a 20 BTC bounty that got me started looking at the bitcoin client code. So it definitely works.
I personally don't think your 20 BTC bounty request is too expensive.
But we still need more discussion, and need more bitizen's involvement to get a real start.
I don't have the imagination to understand exactly how much finally needed, but I'm personally willing to put some money(including BTC) on contribution to a better client.