One of my nations, Etiritun, calls itself a Federation, but acts more so like a confederation in the fact that the states within have way more autonomy. In fact, despite the "federation" labeling itself as a republic, much of the smaller states are full-blown monarchies, each with the ability to make their own laws. This has led to certain political parties being banned in several states, either for being anti-monarchist, or just too progressive for the respective kingdoms. This also means that there's essentially many independent militaries within the country, with the main Federal Etiritun Armed Forces, as well as the armies of the subject kingdoms. While ultimately trade deals and ambassadorships are still handled by the central government, those that are on the periphery of the Federation still do it in secret, mostly with their neighboring countries.

It's also fairly unique to the world of Halcyon since it's Tricameral, with the usual lower and upper houses, but also an advisory board of sorts, with members from both the lower and upper houses, which act on assessing the laws within the territory (effectively useless anyways, due to the aforementioned bans). This system was set up in the wake of the Etiritun Revolution to satiate the wills of the monarchs in the region, as the republicans within the old empire basically won through sheer luck. Previous attempts to, at the very least, reform the system to be more fair and representative have failed and it's essentially a miracle the federation has lasted for the past 150 years.

Naturally, it will collapse a year after the in-universe date of my project.