umm... this game isn't FPS, you might wanna check out Dishonored if you want some nice FPS stealth-action, it's a great game and you can save all you want!
I don't see how not saving in levels is really "hardcore". In this game the levels are shorter (than past Hitman games) and almost work as checkpoints themselves (large "levels" being broken down into several smaller sections, rather than as one whole, uninterrupted area) , and there are still save locations in the middle of the longer missions. It's not unforgiving!
"If we can hit that bulls-eye, the rest of the dominoes will fall like a house of cards. Checkmate"