DOS classes would take considerable changes to adapt to the current structure of the games implementation of 5e. After filtering it down it, a lot of the classes are based on already existing classes within D&D. Unless you are to shoehorn a class in that breaks the paradigm, I don't think it would work well. If anything it may hurt the game. I'm not even a 5e enthusiast and I don't think they should directly add the DOS classes in.
