The historical setting is what makes these games
The best games I've ever played, being able to rule over a historical faction and change the course of history is THE BEST.
I love playing as Poland-Lithuania in Empire, taking over north America and converting all those British colonists to Catholicism.
Or playing as Native Americans and beating back the Europeans.
Or creating your own Satsuma Republic in Fall of the Samurai... this list could go on indefinitely.
The point is, that it is great to be immersed in this kind of game environment, and reflecting on how your actions in game have altered world history.
With a WH:TW, I see this appeal as being gone.
A WH:tw would just be an attempt to peddle to the masses while giving a big middle finger to your dedicated, historically-minded core fans.