Matt that sounds cool. Manicle each nation would name their guild something different due to the fact that each nation wants to have their guild up to them in their nation.
I would speak against that. The factions are already going to be at each others throats throughout most of the gameplay, with limited factions, it'll be hard to form or keep alliances. All of that being said, the guilds would be one of the few things the really tie the group together, a place where platinians, draconians, and all the rest can feel a sense of union. If you take away the objectivity of the guilds, you take away that unison.