I would suggest adding in some sort of bonus xp items like the heirloom gear from WoW or the experience egg from FF3. My reasoning behind this is because once you do a quest, it's gone forever. Right now there are 8 classes to level up. Down the line that number may double. Putting some kind of heirloom gear in via the GC would be a good use of the seals that I'm sure a lot of people have been building up.

Another idea would be set bonuses. The GC gear already has this. It would be nice to see it applied to the more high end gear.