I've only played GRAW and GRAW 2, but with my playtime with other tactical shooters and reading magazines, I decided on some things that would be nice for GRAW 3 (If anyone ever buys it. I doubt it will happen with EndWar coming around )
First, I would like to see more weapons be able to penetrate effectively AND have Thermal Vision added to the game. This would add a new layer of tactical thinking to the game. Plus it would be pretty cool to blast a guy through the floorboard of a building .
Next I would like to have a customization menu where you could decide what you looked like. Choose from multiple uniforms, hats, glasses, skin tone, facial hair, everything. It wouldn't really help the series be more tactical, but it would be cool to have.
Though it also most likely will not happen, Interior combat and destructible enviroments would help make the game more intense, tactical, and cool. If you run into an enemy stronghold, rather than going inside and fighting you could place C-4 on the supports and blow them sky-high!
Everyone of course wants larger maps, no narcom, and more ways to beat a mission. I want that, plus randomized enemy positions. You might run into a tank or Helicopter that wasn't in the mission the first time you played it.