I think masterless (as opposed to masterful) is probably the better option for a classless...class. Keep in mind that there are going to be FIFTEEN master traits, and that each class will get a melee, pistol, shotty, rapid-fire, and all-rounder master each. Giving a class access to every single one isn't so much flexible as it is redundant: sure you could get anything you want, but I'm almost certain the actual class for which it was made is far better at using it. In addition, keeping things mutually exclusive will make balancing these masters much easier, considering that the above case is in no way ideal.
As things are now, the Recruit class would probably stand out by having no masters and no particular benefits (except perhaps an experience boost and better starting gear?), but be the ONLY class to get extended maximum traits at clvl12, maybe even lower. After all, they'll get the best use out of them anyway (and some combinations totally break the game...probably better off if we start limiting all of these player buffs).