I would not see it as a replacement of the current Devfund since BF need stable income, but more of a periodic/if necessary “code-quest” to resolve specific issue/feature.
Thx for the RCS link, indeed this is more easier said than done.
I had also proposed something similar but since I think about it…I think this kind of financing would work better as a periodic thing to help resolve specific and long standing issue as to ensure people doesn’t leave monthly donation.
In any case, I don’t want to derail this topic to a crowdfounding campaign discussion…
Just trying to propose/find solution here 
edit : @dan2 I read through your RCS, there is a lot of very good ideas I think and valid point from both side of view. But mostly I agree with you that this could work…
As you said… A financing system could be implemented inside RCS to crowdfund a proposal… And many others things.