About stealth.
Well, I do agree that there should have been more alternative routs, designed for stealth approach around levels. There were a lot of them in Saudi, but after that not so much. But, no one is forcing you to use invisibility. Sure, its easier, but you don't have to. Just put a couple of points into stealth, enough so that the skill can help you, but not enough so that it makes it unrealistic. You get like, longer awareness, 2 seconds of invisibility before you are spotted, kinda like a warning, I'm fine with that. And put the rest of the points into some other skill, that could help you when you can't use stealth, like in a wide open room full with enemies. SMGs, or grenades, or chain shot, or whatever you find more realistic then shadow operative.
I did this on a a couple of my playthroughs and it was fun. I use realistic stealth when I can, and some other skill when that fails. Also, I did one playthrough in which I was almost exclusively relying on stealth skill, and that was fun too. Not realistic, but what is realistic in video games? And you can't just turn into a ghost and and breeze through a level, that skill lasts for a couple of seconds and then it takes a lot of time to recharge, so you need to use it strategically, when you really must, just like silent running. It was really fun.