I'm not quite sure I follow... You'd have forumites send you orders which you would then interpret, or would you just wander the boards looking for posts that may be re-read in a literal sense as a battle plan? I don't quite know if I understand.
I suppose I'd control the pretender, who wouldn't do much by himeself, combat-wise. They'd occasionally hire a commander, and let forumites claim them, or the other way around. Then I'd just wait for them(forumites) to "make a wish", like give me some troops and send me to X, or get me a magic sword, or whatever else. Then I'd try to transfer those wishes into the game as I see fit, and let things happen.
I'd probably choose two or three "crazy" nations, like Lanka & Jomon(? if that's how Oni Kings nation is called, I can't recollect), so that the silliness would be thematic.
I might wait before I'd start the game, and pass some turns researching stuff, so that there are at least some spells to cast and items to forge. I don't know.
Anyway, an idea, which might be fun, or not, we shan't know before somebody tries it.
Oh joy, so I am attacking a player who is stalling? I shall wipe him from the earth 
Not any more. Ulm became AI controlled as of this turn. Beware hordes of chaff.
