Bruno Heller wrote only 17 episodes.
For me the main question is: did Heller altready know who RJ is or is he trying to find *now* a viable RJ that will not disappoint us too much?
In the second case there is not much we can guess and we can only wait. And hope not to be very disappointed.
In the first case, where he planned a smart plot carefully and planted elements around the whole five seasons, we can try to find who RJ is. I really hope this is the case of course.
In that case, I am pretty sure that Heller wrote the main RJ storyline without leaving the job to his other screenwriters. My theory is that we should filter the seven suspects against this 17 episode list. I would dare to add that RJ was introduced in one of these episodes!
Let me play this game, here is the list of Heller's related episodes:
"Pilot": introduced Brett Partridge
"Red Hair and Silver Tape": introduced Sheriff Thomas McAllister
"Red John's Friends"
"Carnelian, Inc."
"Red John's Footsteps"
"Redemption"
"Black Gold and Red Blood"
"Code Red"
"Red Sky in the Morning"
"Red Sky at Night": introduced Gale Bertram
"Red Moon"
"Strawberries and Cream"
"Scarlet Ribbons"
"Cheap Burgundy"
"The Crimson Hat"
"The Crimson Ticket": introduced Reede Smith.
"Red John's Rules"
Surprise surprise!
Bret Stiles, Ray Haffner, Bob Kirkland were introduced in episodes not written and not directed by Heller! I really think we can exclude them because of this.
So the original 7 persons list could be reduced to:
Brett Partridge
Sheriff Thomas McAllister
Gale Bertram
Reede Smith
Since Reed Smith was introduced just a few episodes ago and McAllister has been a very minor character, I would dare to reduce the list to
Brett Partridge
Gale Bertram
I am a bit disapponited by both of them :-(
Now I just have to guess...
Brett has been a major suspect (the one that even my mom would suspect from episode one...) so to get at least a bit of surprise I would say that Heller went for GALE BETRAM.
Awful, but I fear that can be the result. After many years of guessing... :-(