If it were up to you, which class would you remove from FF? The one condition is that you have to add a class to replace the one you removed! It has to be a class that exists in any other FF game.
Personally, I would get rid of the Monk. Not because I hate the class or whatever, but I guess I just like all the other classes better by default. I bravely made that choice. Ha ha ha.
Anyway, I would add Geomancer to the game. I would have it so the class is more about drawing power from ALL elements. With a game so heavily themed on the whole four elements deal, I think the class with that twist would fit in nicely!
EDIT: Geomancer would be the base class. The upgrade would be called Geomaster. This would give the party access to field commands like being able to sprint and avoid damage floors like in FFV. Naturally, the power the class draws from the elements would increase as well.