Good points made, fellas. What I had in mind was not an add-on to an existing game - what I was trying to imagine was:

What if tw SP and MP got a divorce? So that the next Title(s) released would be China:TotalWar (the Campaign) for say $40

AND China:TotalWar (the Battles) for $19.95.

Stand-alone products.

(Doesn't hafta be China:tw, of course).