Even if a realistic campaign model is out of the question for BTS, I think a map of the theatre showing the battlefield location would be a good idea. When I play a historical scenario, there is no feel for where in the world you are.
Also, perhaps OOB for the entire theatre could be included so that you know you are fighting with a particular unit rather than the generic units that are currently used.
I think this would improve the historical flavor of the game and also perhaps provide the personal attachment to the troops that campaigns provide.