There have been several suggestions for rewards / extensions to the bounty system which I think is the key point here. I think the concern with adding money into the question is shifting the focus of questions such that high rep/knowledgeable users only answer questions with a monetary reward attached.
I'm assuming you've met the community wiki police (always comment with "should be community wiki?") and the homework high inquisition (comment with "is this homework?"). Well, implement this and you'll get "gotta offer bitcoins".
I understand that low rep users might not be able to offer bounties and that sometimes the reward for answering a highly technical question might not seem like enough (+20 rep, say) and whilst I think that can be seen as unfair, I think the balance as it stands is about right. The danger is that in having to have something to trade to get your question answered, you actually lock low rep users out further. That's why bounties are optional.
As to being able to trade reputation for bitcoin, well, bitcoin->reputation would be wrong. Reputation is, from the faq, a "rough measure of how much the community trusts you", earned by participation and no other means. Being able to export it as bitcoin, well, I wouldn't want to. I was hired based partly on my Stack Overflow profile and I think my profile as a whole is probably worth more than whatever my reputation converts to in bitcoins. I see it as a portfolio of sorts and it goes nicely alongside my github.
Besides, bitcoin is such an unimaginative currency name. They should have called it unicorn bucks.