i personally tried to implement clausewitz features in unity. the experience could be summarized in the following points:
- writing stuff on textures is usually slow, really slow, unless the engine was designed with the intention of doing that. as an example, unity forces you to load the texture on the graphic card to render it, and then load it back to the main memory to modify them, which lead to really slow operations since they all move in the system bus.
- writing nice nations names text is almost impossible. Yes the ottoman empire name is usually really missplaced in eu4 but most of the manes are not. i've look for articles and books about how to place names inside polygons but most of the do not use bent text, and they are usually about making sure they do not end up one on top of the other. Clausewitz engine does something different and i have no idea how.
- the standard model of game objects used in many engines does not really work all that well, since clausewitz has to manage 4k+ objects at the same time, and if you are zoomed out all the way they are all on screen.
- independent simulations multiplayer. the engine has to be designed to allow this features. it can't use platform dependent optimizations. yes you can work around that but it's usually better to develop the engine with that idea in mind.
This requirements are pretty much unique to paradox titles, and clausewitz is the only engine that supports all of them that i ever saw. i don't think is actually all that hard to develop another engine that does something similar with the help of a cartographer that knows the tricks of name placement.