Actually, I worked it out to the existing 6, plus two more. I would take the insight from Wis and create a new ability score based on this: Perception
I also would create an Appearance score. Not all creatures would have an appearance score. Vermin do not usually care how other vermin look (that I have noticed), and to the point, it would not really matter to the characters.
Appearance only would fully effect how people perceive a person they have never met, but have seen; after that it would only have half the effect it did previously.
Perception would mainly effect Listen, Spot, Search, and Appraise checks. Just an idea, but I like it.
I also believe a 4th save would be of help--An Awareness save against Illusions.
Any thoughts?