I also have something that may work for all of this, but we will need iterations of testing... whatever dalamar comes up with maybe I can work on adding it to my thing as well.
A private exchange or auction is more complicated. I'd never even heard of a penny auction before discussion here and there seems to be contention, as well as possibly some conflicts of interest between potential users and 'developers'.
I'm all for devcoin goods and services, but personally havent got my head around how to make a devcoin exchange work properly. I think more clarity on what people want - stuff or 'work-exchange' or 'open-source work exchange' etc - then how/why a devcoin platform rather than bitcoin or $ would work, is needed.
That's why I just suggested a basic official bounty site. If that proves to work out, it should give better idea of dynamics. But that's all just my opinion and doesn't stop anyone else having other views and working on them.