I thought that the Assassin's Creed franchise might work as a turn based RPG/strategy game style thing. I imagined a spin off game where you have a team of Assassins with different skills and stats, and you have to pick the best qualified for the mission you are going on. Maybe some are better with hidden blades, maybe some can use smoke bombs more effectively, maybe some use crossbows.
In the missions you have a grid based layout, and guards patrolling the area. You plan out each different Assassins movement and then initiate your turn. Your Assassins move and then the guards move. You have to assassinate set targets, and get XP for stealthier skills, not getting spotted, or fewest kills. You can use smoke bombs to move through areas which would normally be in a guards line of sight.
I think it'd work quite well. It would probably work better on PC or perhaps on mobile touch screen devices.
ANd finally, set it in British Medieval times. DOne. Ubisoft, where's my paycheck?