A crusades sandbox RPG, that’s my pet for years. I bring it up whenever I talk with sb about the perfect game.
It should be dirty and gritty with all the filth and criminals that must have been around to atone for their sins by committing even more. The story might be about upholding your knightly virtues among zealots and political intrigues, but I rather think of a real sandbox experience where you can join any faction or create your own. A M&B-ish approach would also be more modable, since you don’t have to write a good story or care about cutscenes and all that stuff.
If anyone seriously thinks about modding something like that - let me know. I don’t have much experience in modding but I know my way around code and scripting.