Spent about 5 hours just replaying the Paris level on Hitman. All the variations you can pull. It's kind of interesting how the more variations you pull off and challenges you accomplish, the more options are available for how you start out when you replay that level.
I think what they've tried to do (at least from the limited two training levels, and one actual level) is make each level pretty damn big, with a serious plethora of multiple assassinations possible. But because they're fairly chunky, they've established "Challenges" which pretty much list them as possible, so you then have to figure out how you actually achieve them within the game. The more challenges you complete, the more your "Mastery" of the level increases, which opens up options for where you start the level, possible gear to carry with you, if you get a disguise from the start, hidden caches of gear in the level, etc. Of course by using those, you can complete more of the Challenges which increases your Mastery and further provides options for replay... And so on and so forth.