To recieve faster letter replies:
When you send a letter to ANY of the nobles, save your game then immediately 
RELOAD! You will then get the reply in the same season you got them, faster 
than normal.

Unlock Scenarios:

While playing press [Shift] + [Enter] to access the console, then enter the 
following: 

Code - Effect 

unlock_all england - Unlock English Scenarios 
unlock_all germany - Unlock German Scenarios 
unlock_all france - Unlock French Scenarios