Starting a CPA ad network

Ok so I sell a lot of media but never have been on the publisher side. I am looking to operate a CPA network in that I will get impressions from the media and they will get paid on a CPA basis - I then charge that with a mark-up to clients. However, I am not sure about the technological details of this. I need an adserver that will allow me to:

- Measure conversions from one interface to all publishers and give me a report that automates what to pay each (and perhaps even administers the payment through a payment provider such as paypal?)
- The one interface should allow me to set a number of conversions it should work towards over what period, and the ad server should automatically divide impressions amongst publishers, optimize which publishers to do more impressions on based on performance and stop when the number of conversions has been reached etc
- A backend login that allows publishers to see only their own numbers (ie impressions and conversions)
- The backend should also allow them to give a maximum percentage of impressions to my network and plug in other revenue sources such as Google Adsense as a default when no CPL stuff is running

I would imagine these are all kind of standard, but from googling all over the place I couldnt find a solution specifically for my purposes. Can you recommend any?

Also, if they dont want to use my system but just want to give me impressions when there is an offer running; how do we automate that in for instance DART?

Thanks!