L4D Infected Spawning System possible?

So.. do any of you think it's possible to make a L4D infected spawning system using custom powerups that follow the infected to get rid of their initial invisibility + add damage to them? Make the infected do no damage and be invincible until they pick up the powerup..

And the way to stop them from spawning so close to the survivors is have them unable to either use the powerup while in the area around them, or have the powerup despawn.

Do you think this is possible?