I'd be ok with it as either a tank or dps(more in the support dps side analgous to brd/mch) but really hope it's not a healer.

I think support/utility dps (give it some combo of: instant cast procs for magic off of a weapon combo/cast times for fighting from range, enspells, enspikes, some light healing/battle raise/tp&mp refresh) is the best option, as I'd rather see blue mage take the mana tank role.