LOL Sarah dying would be a huge twist given this was all from the perspective of her for the longest. 

My idea of Post-Tournament is just an AU involving Kurama taking more of a lead in being made a detective, whether long term or short term, in order to offer Yusuke a break after the tournament. Everyone's already so strong post-series, we'd need something big for that, something ridiculoussssss. A mystery sounds more fun than just a demon blitzing but we'd throw those in there too :3