Okay guys, this has to be done...
I've been lurking q2a script and without this plugin, this script is a bit less.
Plugin needs to contain these features:
1) Custom user field where users put their own Adsense ID.
2) The ads will be shown only for best answers. So, who gives the best answer, gets the ad clicks.
3) Since Google doesn't allow ads from different acounts on the same page, there should be a ad rotation system can be controlled by admin. 1/1 (1 time user ads / 1 time admin ads) ad show ratio seems fine to me.
I may pay a bit for this plugin. Someone should do this immedietly! :)