Okay...not really Bob Kirkland he is obviously dead, but I'm listing this under Bob because Red John is...

Bob's twin brother.

There was the random story by Bob last week about his twin brother who started getting involved in a cult and disappeared.  No body found.  That's because Bob's twin became the cult leader, Red John.  

I just found it strange that Bob's brother was a) a twin, and b) body never found.

Technically, Jane could have met Bob's brother in the past (that was the one RJ clue he had to go on, that he "shook hands" with him in the past) if Bob's brother was impersonating Bob at some point.

There needs to be a surprise, more than just slowly whittling the list down to one.  And if they throw out EVERYONE on the list and it's someone not on the list, well it's cheating and would be horribly unsatisfying.   So...someone who is on the list (even though Jane doesn't realize it yet) and fits the bill of a surprise villain and a good Red John (really, the only two good RJs left are Malcom McDowell and the Sheriff...Bob was good but dead, Brett was good and creepy but dead...FBI guy boring, Reed Diamond and Bertram are cool but not really RJ brilliant.)

Bob's twin brother.  That's my two cents.