it think its Bret stiles but furthermore I believe he has van pelt under his wing with him  ...Only 4 people knew of Janes happy place in s1e6 about 17:30 in he revealed his happy place to only the team .. I think with stiles and van pelts connection they seemed to make the most logical sense of the 4 .. I also find it curious the timing of her and Wayne getting back together. Stiles has the brain, Money, And mind influence to be RJ he does run a cult after all ...he knew fry's location , has many cops and local enforcement in visualize and seems to really like Patrick and had the power to break out martin which would take serious law enforcement corruption and pull to pull off ..