IMO, race, classes, story, and professions should be among the last things to design. I'm sure those can easily be added later into the engines once the big things are in.
How combat works takes much much higher priority. (for example)
I'm temporarily suspending this project to work on my 2D RPG game, not an MMO, based on a Final Fantasy battle system. It's called Eternity Flower, if I'm bored I'll write up a design document for it too :P