Rigsby is Red John & has seduced Van Pelt to be a follower.  I imagine the real manipulation occurred after she killed her former fiance.  He is good looking and charismatic enough to manipulate, especially after forming relationships.  He has always been the supposed dumb/nice jock of the group to hide his true diabolic mastermind nature.

Under this theory:

1.  It meets the Keysor Soze theory, because no one would suspect Rigsby (too nice, naive, second fiddle to Cho, etc).
2.  Would meet the amazing reveal criteria, because it reveals not one, but two members of Janes CBI team as villains.
3.  Rigsby fits the physical criteria.