Keeping things simple makes it easier to modify them, not making them strong.
5 stages is too many, it's too much to learn and too much to write, for a system that will need to be reduced. Why bother making all those, when the last three stages are the only ones anyone will care about?
Likewise, why bother with different symptoms for different insanities? I'm not sure, but I'm pretty confidant that your insanity isn't currently decided until you actually snap. Changing that is a lot of work for a fairly minimal effect that, as people have stated, shouldn't be that predictable, anyway. Urist McBorderline just needs to show some sort of symptom to indicate that he's getting close to the edge.
It's silly to say that this is too minor of an advantage to count, this makes infinitesimally easier something that is actually pretty easy once you figure it out. In point of fact, the added complexity will make it slightly harder for non-wiki newbies to figure out the system. The purpose of this is to make moods more interesting, and to give the player some information on how well he's doing. Simpler is better in every respect.
That said, these are crazy people, and it'd be nice to give them a little spice. So, I'd be cool to have your symptoms randomized, like the rest of the world.
Currently there are only four funny moods, and it'd be nice for them to gain a bit of variety. You could have your Fey mood with a side of facial twitch, or a Secretive mood with a bit of unintelligible mumbling.
If the symptom change at the end proves too confusing, have them gain a second symptom, instead of just switching their symptom out. You'd have to check against duplicates of the same symptom, though.
For extra Fun have the advanced symptoms overwrite the material requests, hurting players who have forgotten what that guy wanted in the first place.