Well, instead of deleting them you could retire them and use them when needed by respecing them a little with Hover/fly, some invisibility, a green smoking tendril aura costume with lots of drab gray and black and TADAAA! you have a Ghostly hero that can run roleplaying events for your friends that involve a message from the great beyond (like bringing his or her killer to justice).
Plus, the hero can always come back from the dead to help your SG with missions