Yep I had the bright idea of doing this but it's totally beyond the head unit I'm afraid.
If you want to change from one to the other , allow around 5 mins spare , turn the car off, turn Bluetooth off, turn car on and remove keys , connect iPod , go into settings , change connection type to OTHER and the iPod icon should be enabled. Then once you have iPod connected enable Bluetooth on the phone. You can then enable the hands calling if required.
To be fair its stupid when you think this is a car radio designed to be used while driving, pioneer forgot that.