For a Game Center based game what is best way to add A.I. computer players?

I want to allow the user to create local games with computer players and also add computer (AI) players to online games as well.

Could they ever show up in the Matchmaker? What about the request for min/max number of players?

How would this be best accomplished? Could guestIdentifier be used for this purpose?

I'm thinking now that I'll just make my own view of the matchmaker list and will just internally know which player is the active one.