Does anyone know how to set a home point mid-air mid-flight so you can get the Phantom to circle around it in HOME LOCK mode, but not have the drone forget where the pilot is should the phantom lose connection or battery level get too low?

As I understand it, the Phantom Assistant app dynamically updates the home position.  Should the pilot move from the takeoff location the drone will return to the last known pilot location.   This same location is used by HOME LOCK to get the drone to fly directly to the home point or circle around the home point.   I think the dynamically updated pilot location is great but I'm wondering if there is a way to remember two reference locations,  1) where the pilot is now and 2) a SECOND HOME POINT established mid-flight to be used in conjunction with HOME LOCK MODE so you can get the Phantom to easily circle around this SECOND HOME POINT, some interesting target selected in flight (for example a building or monument).   

cannot be done on this flight controller. This is a feature of the A2 which is the pro FC from DJi.
you can set a home point in the air on the phantom, however it will return home to this position rather than where you are if invoked.

the naza cannot rememer multiple home points, neither can the A2 for that amtter but the A2 has a POI ( point of interest ) feature and is a high end controller.

Yes, Phantom doesn't support for dual reference points. Dynamic home point refers to that when using a GPS-enabled mobile device and running the VISION app, the Home Point will automatically be reset to the location of the device every 2 seconds during flight. And only the latest updated home point would be remembered as the home point.