1) There is a spy only when there are over 10-15 people to prevent anybody being the obvious spy.
2) Warn a player he is a spy 25 seconds before he becomes the spy to prevent any annoying spawn killing in the beginning of a round.
3) Only a King or a guard with a new perk (3-4 points) can kill the spy in order to prevent the spy from being killed or shot at by too many people.
4) Once the spy dies from a guard or a King he should spawn as assassin.
3. When nobody has the perk? He could just kill everybody...