Original world building is one of the virtues of The Goblin Emperor. The elvish government is one facet of this. A key example is the Corazhas, which might be described as an independent privy council with teeth. Evidently, the emperor needs support from at least half of them for important actions like building a major bridge or appointing his own chancellor.
As far as I can tell it is an original invention of the author, without any actual historical prototype, but it seems workable enough.
There are seven witnesses. The parliament, magicians, clergy and universities each appoint one. One comes from the treasury, one, The Witness for the Foreigners, from what seems to be the equivalent of the State Department or Foreign Office, and one from the judiciary. Apparently, the last four aren't simply appointed by the current emperor, but chosen by senior civil servants and judges that were, in the case of a new emperor, appointed by previous administrations.
Not a democracy, but an interesting set of checks and balances. One can see how it might have evolved from a more purely advisory council.