From the looks of this forum, it looks like most of the people here are interested in the multiplayer aspects of the game, that's not me. I'm interested solely in the single player campaign and would love to see another Uncharted game, but as the series has progressed, it's seemed to move away from being an action/adventure game to more of a run and gun shooter.
Here's what I propose...
Rather than having difficulty levels for the game, have a couple of different modes:
Adventure - Play through the game concentrating on the puzzle, exploration and platforming elements. There should be less enemies. Where there are enemies, it should be possible to complete the area with stealth and enemies should react realistically to being shot (i.e., if they are shot once, they should probably hit the ground).
Gunplay - More like what is in Uncharted 3 and the latter levels of Uncharted 2.
The same trophies should be attainable in each mode.
What I describe as Adventure mode, could well be similar to what is currently the 'Easy' mode on the game, but I wouldn't know since I have an aversion to playing games on 'Easy' mode! Semantics could make all the difference here.
Anyway, just a thought.
Those are good ideas, OP
For myself, while I find the enemy AI pretty good, they respawn the exact same way time and time again. ND needs to have more dynamic enemy movement and spawning. No two playthroughs are identical