This may be a bit late but I did have a norespawn mod from a long time ago. To get it to run, just load it like any other Nolf 2 custom map or mod.
There are a few caveats to running this mod in single player but you can read all about those below or in the included extra-info.txt file.
Here's how you turn respawns off:
1. Install WinRez LT Studio
2. Run WinRez. Open an existing file and select GAME.REZ.
3. In WinRez, select the ATTRIBUTES folder and extract AIGOALS.TXT.
4. Create a folder called 'nospawning' in your No One Lives Forever 2 directory, then create another folder called 'attributes' and put this inside the 'nospawning' folder. The folder structure should then look like this:
5. Open AIGOALS.TXT, and delete the lines below '[GoalSet9]', up to and including 'Goal5 = "Menace"' (leaving '[GoalSet9]' there). It should then look like this:
Name = "Guard"
RequiredBrain0 = "Default"
RequiredBrain1 = "Tulwar"
RequiredBrain2 = "Bystander"
RequiredBrain3 = "ViewMaster"
RequiredBrain4 = "Police"
RequiredBrain5 = "Terrain"
IncludeGoalSet0 = "DefaultRequired"
IncludeGoalSet1 = "DefaultBasic"
Goal0 = "Guard"
Goal1 = "Sniper"
Goal2 = "Work"
Goal3 = "Menace"
Name = "SuicidePatrol"
Exit AIGOALS.TXT and save.
6. Move AIGOALS.TXT to the 'attributes' folder.
7. Go to the Desktop, right-click on the NOLF2 shortcut and select Properties. Add ' -rez nospawning' (minus the quotes) to the end of the Target command line, so that it looks something like this '"C:\Games\No One Lives Forever 2\NOLF2.exe" -rez nospawning'.
8. Play the game.
IMPORTANT: After completing Chapter 8: The Art of Murder "Crossfire", you must remove the ' -rez nospawning' from the end of the Target command line before playing through the next level, The Art of Murder "Invisible Walls". Respawns are required in this level because Armstrong won't open the exit until a certain number of enemies have been dispatched. The Target command line can be changed back to ending in ' -rez nospawning' once "Invisible Walls" is finished.
You'll also need to do the same thing after completing Chapter 14: Endgame "I think we should presume she's failed" and before playing through Endgame "Man-Handled". The Target command line can be changed back to ending in ' -rez nospawning' once "Man-Handled" is finished.
The only minor problem with this method is that you'll occasionally encounter some 'lobotomised' henchmen. They just stand there and don't actually react to you, but can be killed if you shoot them. These enemies are the ones that would've respawned if respawning is enabled. They'll only appear once, and this doesn't affect the regular i.e. non-respawning enemies, that you encounter. So all it means is that you have a few easy targets to kill, if you wish. Otherwise, just ignore them. This is a small price to pay, and the lack of respawning means that you're finally able to play the game stealthily, since you don't have to worry about taking your time on a level, sneaking around and then getting shot in the back.