I agree, somewhat, with getting rid of common and using the human racial languages as a foundation. I do have regional and national languages that fill the void left by common though. Keoish draws heavily from Suel and Oeridian, with the dialects spoken in Geoff and Sterich mixed heavily with Flan words. In areas of high demihuman populations, their languages will be borrowed from for human common as well, and as I mentioned in another comment, the 'lower' humanoid races usually speak a corrupted form of whatever local languages are common.