I did a search on the health regen and I can't find anything conclusive. But every time the game has been shown it's with health regen, and without healthbars or rations. Given the backlash I think they would have said something by now if it's up in the air.
The idea of removing some things with higher difficulties has been brought up before, and I think it's a bad compromise. I'd rather have one set of game mechanics for every difficulty instead of locking mechanics away at higher difficulties. Let me choose what I do or don't want to use regardless of difficulty.
I like that they are still taking feedback on this. But it does make me wonder how strong their own vision is. Are they adding things like the open world because they think it works well for the franchise, or did they just want to make an open world game that they struggling to fit to MGS. It doesn't help that MGS5 looks like a very odd mix of ideas right now.