Well, what if it is Bob Kirkland's twin brother? He was never found or shown in any episode. All we know, according to Bob Kirkland, that he was murdered by Red John. What if the twin brother manifested the whole "murder" thing to stay invisible, and actually ran the Blake Association?

I have read few of your theories regarding Red John, and they all sound very plausible. But I have to go by hard evidence given in the Red John Preview (final episode). Just tune in to 0:18 of the preview. Think hard - who does it sound like when the voice replies to Jane? Bob Kirkland, right? If you are not convinced, watch few more times, see if you can associate the voice with Bob K?

So, if Bob Kirkland is already dead, but the voice sound like Bob K -- then I have to go with Bob Kirkland's character.