Stellaris Zero is a mechanics overhaul mod focused around overhauling the internal management aspect of the game. With everything from political parties to pirate empires to redesigned rebellions, the goal is to improve upon the under-utilized systems in the game. Mainly, factions and governments.
The initial release. It won't be bug-free, but it's working!
If you're on moddb, I'm assuming you at least know how to look up a tutorial on installing mods.
Stellaris replaces some core files that most other mods reference. You can try using SZ with another mod, but I doubt it will work smoothly.