Is Elmo a pure fighter when you first meet him? I recall some discussions about Ranger, and there are some old guides stating he levels as a multiclass Ranger/Fighter. I don't see any favored enemies in his feat list though.
Straight Fighter. He used to automatically take levels in Ranger on level-up when the game controlled NPC levelling.
Ranger would be cool, haven't found a ranger npc yet, but then again haven't looked very hard. What would be really cool is some dialog triggers revealing Elmo's (and/or Otis) ruse and true mission. Maybe they are in there and I just didn't get him to sufficient level.