I think Psionics can work as an alternative to magic. Think an order of Monks who's self appointed job is to deal with Mages who get too powerful and begin to mess with reality. If rare enough it can make a great DM tool to make it harder for the party to detect what thier enemies are doing. DM just has to treat it like clerical or arcane magic. Consider what can be done and what the other orders of the world can do about it and what the Gods will do about it.