Personally, I don't like the idea of the hardcoe mode. I played FO3 with mods that added similar things and it was pretty much a chore to play the game; you spent more time taking care of your personal survival than actually playing the game. Now, it is probably more balanced in NV, but I still don't have any desire to try it.
I, however, thought that it would be cool to have a throwback to FO1/2 players by adding a game mode that makes the game turn-based like the original games. The camera angle would just be locked a set distance above the player, tilted at a 3/4 top-down view (isometric, but it's a fully 3D game world so it's not true isometric) and the interface would be more like the original games. Outside of combat, not much would have changed. You could still use WASD to walk around, but you could also click with the mouse to pick things up, move, talk to people, etc. When combat starts, you're limited to using only your Action Points for everything. If you move, every step is 1 AP. Attacking would bring up VATS and use pretty much the same AP as weapons do now.
This probably can't be modded in, but if there is a way, someone should try. It would be like Van Bueren, only with better graphics and, you know... It would be a complete game