I like this idea.

As cool as some of these specializations' names sound, though, particularly in terms of defining your job (Mystic Knight? Heck yes, that sounds like the kind of job I signed up to play!), I can't see the names themselves able to see very much prominence within the game's programming. I see a level 99 Red Mage, and without keen observation of said Red Mage in action (or being explicitly told), it would be difficult to figure out whether said Red Mage has taken a "Time Mage" path, a "Mystic Knight" path, or whether said Red Mage had only just reached level 99!

Still. Very cool idea, nonetheless! There are potential problems where one build on the surface seems like the more obvious choice than the others, but if S-E has learned anything about game balance (as if, right? >_> ), I'm sure there will be enough incentive for even the off-beat builds for at least a few adventurous players to play around with them.