My suggestion is to create extra slots in games with observer mode for observers to join the Legion or Hellbourne teams. These observers would only be able to see what their team sees (in the case of a Dark Lady ultimate, they'd see nothing). There would also be the usual all-seeing observers for referees, casters, etc. Team-aligned observes fill two roles:
- They allow someone who's too busy to play HoN, or who is the sixth player on a team, to watch his teammates play without opening up the possibility of ghosting. This is particularly important in tournament games where there are frequently observers from one team or another, and ghosting is occasionally a problem.
- They make it easier to coach new players
Adding team-aligned observers would have no effect on games without observers, and would not replace existing all-seeing observers.