Combat

A nemesis system for Skyrim: lose a fight and you wake up hurt, while the one who beat you becomes a named rival who took your gear, ranks up and hunts you. Beat him to take it back.

A fighting pit for your own followers: sign them into your Coliseum, pick your line and watch copies of them fight from the royal box, 1 v 1 up to 30 v 30. Fighters level up fight by fight, and the fallen are gone.