nice work AHO, I'll test everything as soon as I can!
I've read about gameplay simplification, about the possibility to know down some NPCs from the front; in my opinion, this could simplificate too much the nature of the gameplay, since the high difficulty is a part of the game design. so, it's good to have this feature, but it could be more realistic to add an alert level using it; after all, if you are knocking down a person in the front, at least he should scream, no? To avoid it, you should hide and hit on the back, and everything respect the nature of gameplay.
A tedious gameplay characteristic you should manage, maybe, it's the enemies exploding granades when hit. It is not realistic, since they do it even when they haven't seen you before. At least, it could be useful to make them recognizable on the map, if it isn't possible to manage this.
Last idea, is the possibility to use the clothes stained of blood (like on the Hitman saga). Again in respect of gameplay nature, this feature should be added but not whitout is problem... maybe making the alert level rising faster when in prossimity of enemies, after all you won't shot immediatly a colleague only because his jacket is spotted of blood, no?
However, gameplay changes are welcome but they should be optional or selectable from the game menu (this last possibility is better of course).