Raspberry Pi Bluetooth A2DP and HFP

Hi. I am currently wanting to make my Raspberry Pi B Model into a "Car computer" of sorts. The current progress on this project is already about 50% with alot of work already being completed but I need assistance to slightly modify it to the new revision of the project and to finish it off as there have been some changes now. Originally the project was to have my iPhone able to stream audio via Bluetooth A2DP to the raspberry pi which would then output it through a USB sound card with an aux cable going to the car stereo. However I now wish for the iPhone to use A2DP and HFP(Hands Free Phone) protocols to connect to the bluetooth dongle on the raspberry pi which will then relay all audio/phone calls using a secondary bluetooth dongle to the Car Stereo (In small terms using the raspberry pi as a middle man). A USB sound card will be used to input a "Line In" Audio device which will inject its audio stream into the stream going on the second Bluetooth dongle which connects to the car stereo (hope thats not too confusing!) Regarding connections for power to the car, that is not neccessary and I have handled all of that to allow safe power up and power downs. The finished product should be as follows: Car turns on > Raspberry Pi turns on with it > Raspberry Pi auto connects to iPhone using first dongle > Raspberry Pi auto connects to car stereo using second dongle > iPhone automatically senses bluetooth connection and starts playing music to the raspberry pi > Raspberry pi integrates the line in audio with the bluetooth audio from the iphone and seconds it through the second dongle to the car stereo. Headunit buttons to skip and goto the previous song as well as fast foward should continue to work as they currently do. AVRCP (Metadata) should also be displayed still as it currently does. When a phone call comes through, the phone call should output through the car speakers and utilise an external microphone plugged into the back of the JVC headunit (The microphone has always transmitted back through its bluetooth device to my iPhone so should be possible, failing that I have a second USB Sound card which can be used for an external microphone). I currently have to use for this project a: Raspberry Pi B Model (Early model) 2x Bluetooth Dongles 2x USB Sound cards (Both have 1 output and 1 input) 1 USB hub Please contact me for further information.