It seems there is an other way: http://www.sysinternals.com/Utilities/Junction.html
This tool allows you to create softlinks on win2k and upwards when using ntfs. You could link a maps directory into your Nexuiz dir and start nexuiz like: nexuiz.exe -game maps -game data then it will load files from both directories but thanks to the -game data (must be the last -game thing) it also works online..