I agree with there Red, well said.
Anyway everything that I would have said has been but it sounds quite interesting having players with specific role.
and on a sort of unrelated note I would like to see a much longer ranking system Halo 4s was too short even with the specialisations I competed it by December 2012 While Halo Reaches I still have to finish.
The point is I would like to see them return if 343I makes Halo 5 more about Specific classes like TF2 maybe if they make it like Halo 4 and not at all if Halo 5 is like Halo 3.