Firstly, the balance of power is not an artificial standard of balance towards which everyone will work. Everyone will try to make themselves stronger, but to make one stronger, the others have to be weakened, and as everyone tries to do the same, they will hold everyone else in check, creating a balance, until one player or one faction becomes too strong to be contained like this. When this happens, diplomacy and alliances will change, until a new balance is found. This is true for all games played within the scope of realistic actions.
Secondly, the news paper is more like a collection of official declarations. And even in the medieval times, state declarations were made. But since these declarations are meant to be circulated inside a nation only, they can be framed accordingly, without addressing other nations. They can address only the people of the same country. Such notices are easily procured by the people of other countries as well.
Thirdly, communication in the medieval period is indeed a difficult thing. But it would be perhaps unnecessary to cancel all communication with other states, as in the game, you are given a degree of knowledge with regard to other states anyway. You can set a standard on this as you may please, but a complete cancellation will be unnecessary.
Of course, war will be more common in this period. That shouldn't be a problem.
