I do not force players to play any way, this is the way they choose to play and my problem is the system doesn't support it. Yes you can make something like the last chancers or a group of specialists but there is emphasized to the point where it is difficult to play the way the guard is portrayed in the fluff.
Bull. No one is making one of your players play a Commissar or Ratling or Ogryn. You're just irritated the option is even available, I'm guessing because your players are in fact interested in playing those specialties and you're stuck in the position of having to tell them no.