Well, Mafia's really complex, and we've only just begun.
We haven't even delved into scenarios.
Or fluctuating roles as the Days progress. Imagine if a VT were, Day 2, given PM instructions to get some other player lynched, or else Scum would gain the ability to jail people?
Furthermore, if you guys want to get really advanced, there's multi-factional groups within Town AND Scum. There could be multiple groups within the collective "good guys," but they're quite alright with killing each other if need be, or if it's better for the greater good. And I could always swoop in and give someone a vial of poison during the Day...