I have a few ideas for free play. here they are.
1. Let the dummy's walk into random places.
2. Let 1-3 dummies be an imposter and if you walk past them, they will have a 30% chance to kill you
3. Let dummy's do task and when they are at a task, every second that past by, there will be 20% chance that the dummy will complete it.
That is all my ideas for free play.