I am a fanboy, so take the vitriol I will spew with a mountain of salt (not that salt will help with that /chemistry joke):
Degrading weapons are ALWAYS a horrible idea, and so is only being able to use a single one. Having combat is fine, and so is having no option of fighting back (like Amnesia), but limiting it is just an awful idea. The tension doesn't revolve around your impending doom, but whether or not there is another pipe around that can replace the current one with 5% durability left ('cuz, ya know, metal pipes break so easily).
QTEs. Stupid idea, I thought we've established that by now. No game has ever been fun if a stupid "Press X to not die!!" suddenly appears on the screen. If the entire game is QTE based, fine, but mixing always sucks.
The Protagonist. Having a prisoner isn't exactly a good idea. Where's the subtlety? Hell, we know he did something wrong, so him facing his inner demons won't exactly come as a surprise. Him looking like a mix of James and the bloke from SH4 doesn't exactly make him more appealing either...
That clue system will diminish the story by quite a bit. What I liked so much about SH2 (best game EVAR, etc and so forth) was that the story remained constant, but your actions determined James' future. It was his struggle you were witnessing, him coming to terms with his actions. I don't think the story could be as masterfully told if this linearity is removed.
Ok, now that I've got the hatred out of the way, I have to admit that the trailer actually looks quite good. I also don't have any problems with the water thing, provided it makes sense. Oh and finally, please dear developers, look at SH: Homecoming. That's the perfect example of how to NOT make a Silent Hill game.