Someone mentioned it yesterday I think, and I agreed strongly with their idea, and that's that there should be a Mongol DLC that adds more events and choices to their arrival.
Contrary to the image of solely mindless, blood thirsty monsters, from what I understand the Mongols did send emissaries to lands before they invaded...it's just it didn't usually end well, as is the case with the Persians and their 'mishandling' of the Mongol messengers. :unsure:
So it would be great if there was a system in place that gave the player, should they face invasion by the Mongols, the choice to surrender to the Mongols and become a vassal, or resist and...as we all know...likely be destroyed.