This all seems very disorganized. Co-operation is needed to build a comprehensive solution. Perhaps a modular session border controller where one module is Openser and the others are a B2BUA and a media proxy. They would be optimized to work well together, possibly using non-sip communication. They could also be used independently. The building blocks are available they just need to be tweaked.
OpenSer + MediaProxy + Radius + CDRTool provides a complete and integrated solution (except Sessiontimers).
What's your call limit? what is the maximun calls you can take with one media-proxy? 100?