I've had a look at The Balancer Reloaded. It failed for me, complaining that /Art/Units/Nomad/ScoutRunFoot2.wav is missing. I imagine that's what you saw. I confirmed that there is no such file in the mod. There *is* a ScoutRunFoot2.wav file in the main Civilization III Complete/Civilization 3 Game Data/Art/Units/Scout/ folder, and so my first try was to copy that file into the /Art/Units/Nomad/ folder in the mod. That didn't work - I still got the same error.
I then tried copying some more files from the standard /Scout/ folder into /Nomad/, and the problem moved to a Worker file. So I copied the entire contents of the standard /Worker/ folder into /Nomad/, and I was able to start a game.
The basic problem is, I think, that the .INI file for the Nomad unit defines a number of .amb files that tell CIv3 how to combine individual sound clips to create a complete sound sequence for a unit action - walking, building a fortress, etc. The .amb files are binary format files that contain references to .wav files which are the actual sound clips. The software tries to find these clips in the same folder as the .amb file, but it may also attempt to track them down in other locations. It appears that the search paths don't include the /Civilization 3 Game Data/ folder.
I have no idea whether what I did will allow an entire game to run. I suspect there may be other units that have similar problems. However, maybe this will provide a starting point for working out how to get it to run.