I think Ray Haffner could be RJ. He wouldn't harm Lisbon because he really likes her, and he calls her Teresa, just like RJ did in his phonecall to PJ the day BP was murdered. Who else calls Lisbon Teresa? I'm planning on reviewing the whole series again for this, unless someone knows this already? (He is an excellent whisteler and is of the right age and bodytype etc etc)
Still have some untied knots about Ron's role, and the reason of Wayne and Graces "disappearence" from the series....