We've had Fullbringers pretty much from day one. They're just lumped in with "mediums".
So at least I wouldn't be opposed to a character drawing from the canon concept of Fullbring. It's well within parameters of powers other mortal characters already have.
@horngeek: What would you like me to do to the NPC 4th Seat twins? Move them up or down a rank in the registry list, or write them to be "away?" EDIT: technically, I suppose they could still hold the same rank. The idea of multiple officers of equal rank is not foreign to the game, after all.