problem is they can't really give new jobs with different roles to existing classes without altering the abilities of that class. SMN/SCH only worked cause they gave ACN skills that were not useful for DD purpose and having the pet do some of the work. So they likely have to add new classes to add stuff like samurai, ninja, dark knight and so on (or abolish classes eventually and just go with jobs)

You could do a lot of unique stuff with samurai but making it a tank will probably end up being what just another mitigation tank.