Let's start with a quote from Eorzapedia:
Yoshida-san is between two possible plans at this time. The first idea is that the traditional names would be introduced as “higher” or “advanced” classes. The traditional classes would thus be something of a goal for players. The second idea is that the traditional names would be more of a subset or specialization within the existing classes.
In the OP - Key words there. I'm just laying out a way that it can be done while trying to take into consideration balance. Balancing is probably something best left for them but its important enough that I feel it should be mentioned and we should discuss it.

And +1 to Demacia. I checked that for a reason as well.