From a player's standpoint, it could be more beneficial to be patient and cross that bridge when you come to it. Personally, I only intend on getting one of each Atma with the jobs I plan on using the Atma with.

Though in all honesty, about the new classes, I doubt "Thief" will even be a class, per se. Looking at the structure of how classes are thus far, there is not a single class in the game that is modeled after a traditional Final Fantasy class. Some may share names (There were Conjurers in FFIII, which were basically less powerful Summoners, and Gladiators were a secret Job in FFV Advance), but for the most part, they aren't really anything more than catalysts for the actual jobs.

If I were to formulate a theory, I'd say that "Thief" will be a Job rather than a Class, focusing more on stealing and such whereas its counterpart, Ninja, would focus more on powerful DPS. As for the actual class, it would probably be focused on a "Rogue" class or something similar, which would dual-wield daggers and focus on skills related to that form of combat, and perhaps even rival Pugilist in terms of speed, or maybe even have some stealth elements to them. I just can't really see "Thief" being the initial class, especially with how the other classes and jobs are set up.