It's possible but not like that.
ALL races with skills must be in WCSraces_db or they just wont work.
ANY race can be copied out of WCSraces_db into, say, WCSpublicraces_db or WCSprivateraces_db. This can be done 100% automatically. You only need stuff like name, reqlvl, limit, key, etc.
You can then make a menu which picks races out of WCSpublicraces_db for changerace or WCSprivateraces_db for changeprivaterace.
You then need a link from WCSpublicraces_db or WCSprivateraces_db in order to get back to WCSraces_db to set to the correct race in order for everything else to work around it.
I've done it but I'm a greedy bastard

I don't mind helping out to some extent though. I can provide you the keygroup creator if needs be but the rest would be up to you as I can't remember all the little changes I had to make in order for raceinfo and privateraceinfo to work with it as well.