You could also do another take on the “nested murder” scenario and do it in a way that encompasses more than one mystery, but requires information you’d only know after subsequent playthroughs i.e. solving one mystery gives you a clue to a larger overarching one. It would be a nightmare to code, and I’m not even certain how I’d structure it to make each mystery justify another playthrough and still make narrative sense, but it might be interesting at the very least.
