Well, new factions will be added, from what I know as soon as we stabilize and run without problems the latest files sent by Korinov. As for desert territories, if the map has them, I think it's just easy to expand it in order to have them. If the map doesn't have them, we will see what can be done.
For diplomatic messages, it's a very good suggestion, but I will have to research it, because I don't know how it can be done so.
Now, for the Crusades function, there was, I think talk of such an event and I have shared my thoughts on it before. Generally, it'll be easy to call such an event in a specific date, involving certain functions or creating new ones after that is called. Adding a random Crusade, in random dates or after something we set as parameter is achieved is also doable, but of course, it will not be historically accurate.
Also, you have a YouTube channel? I want to subscribe.