This is a campaign/rules/style conflict.

My take on the game is that it includes everything we've seen; but that there's a lot of room for expansion. (i.e. Harry hasn't seen everything in the supernatural world...or the real world, for that matter).

One of the players (who's been thinking about being a co-GM) is big on Rules As Written and doesn't want anything in the campaign that's not in the books.

The big sticking point is psychic powers.  One player wants to run a psychic with powers not listed in the game book.  The possible GM/player is very much against this.

The power in real question is telepathy, a standard psychic (if not seen in the Dresdenverse) power.  With proper limitations, I felt that it wouldn't unbalance the game, nor ruin the adventures I had vaguely in mind.  He feels very much otherwise.

Primarily, I see the Fate system as allowing a lot of cool things for the players; of me saying Yes as much as possible when a player wants something (and explaining why the game will be better for the group when I say No when that's required).  Am I reading something that isn't there?