Here's my latest working definition of public diplomacy.
The purpose of public diplomacy is to identify, empower, encourage (and possibly equip) self-organizing systems. The self-organizing systems engaged should be those that currently or potentially support, directly or indirectly, the foreign policy objectives of the public diplomacy-sponsoring actor. The support networks of groups that oppose or compete with the same foreign policy objectives should also be engaged as minds can be changed.
Your comments are appreciated.
Whats wrong with: diplomacy aimed at foreign populations rather than governments? Methinks you're getting too complex.