Is the Khan declaring war on a Fallen Empire an event that takes into account how strong that Fallen Empire is? Because in my current campaign mine come with attack moons. That's kinda a bit too much for the Khan to handle.

The event unfortunately does not take into account how strong the Fallen Empire is. I will work on that so that he is at least equivalent to the FE before declaring the war. Might take a little bit though.

I would like to see full compatibility with Zenith of Fallen Empires. In other words, if you’re an Ascended Empire, the Khan will be just as cautious about picking a fight with you as he will be with a Fallen Empire (I.E. he holds off until he’s conquered the rest of the galaxy and is sure he has a reasonable chance of winning). Maybe even expanded diplomacy options for Ascended Empires, like actively collaborating with the Khan to destroy Fallen/Ascended Empire rivals in exchange for a non-aggression pact or even a Federation of sorts. A ‘we can rule the galaxy together’ sort of deal.