Holy crap! I feel stupid after reading all of that (I'm new to kixstart and scripting). I too did a little work on a script to update NAV defs. You'll probably get a laugh out of the simplicity but....... we'll thats pretty much the only reason I'm posting it.

@IF not exist %SYSTEMROOT%\1024i32.nav \\server\antivirus\updates\1024i32.exe
@del %systemroot%\*.nav
@copy \\server\antivirus\updates\1024i32.nav %SYSTEMROOT%\

the *.nav is a file I made

I'm sure cavemen have written more complex scripts than this one, but hey you gotta start somewhere.