[geoschmo]

Originally posted by General Woundwort:
One word of warning - any mod must have 20 (not 2) major races in its "races" folder, or it will do goofy things (like run duplicates). Any two player games would probably have to be set up manually.

You can avoid the problems this causes by including the stock race folders in the mod races folder. You don't need the files in the race folders, except for your new races and any files in the stock races you want to change. Just the empty race folders is enough to let SE4 point back to the stock races for what it needs.