The System is easy: A character (Bandit in the example) is activated behind the bound border with an "act" and zero lifepoints. Even the enemy counter doesn't acknowledge it. Next, this character activates a criminal and goes to a frame with an unreachable bdy (7000 in the example).
Now you have to configure this to a Multi-Criminal - one bdy for characters which are allowed, another for characters which are not allowed. If the bdy for allowed characters is hit, the criminal goes to a frame with an itr which hits the bandit, the only man in the phase dies and the stage continues.

To guarantee that the system works, you have to set the itr that hits the criminal in a few different frames, depending on if the character is allowed or not:

-Allowed:
  itr:    #authorised
   kind: 0  x: -5000  y: 5000  w: 10000  h: 500  injury: 100  zwidth: 500
  itr_end:
-Not Allowed:
  itr:    #unauthorised
   kind: 0  x: -5000  y: 6000  w: 10000  h: 500  injury: 100  zwidth: 500
  itr_end:

In this study example I only modified Davis and Julian - Davis can play the Stage, Julian is not allowed.

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Inspired by MH-Razen and YinYin