There has been a certain moment of time where me and dustole (player of Allison) planned something vaguely similar for the Morek area: a set of single duchy states all confederate and forming a single bloc spanning Flowrestown, Unterstrom, Donghaiwei, Muspelheim, Aegir and Springdale.
Now, without going deep into the details for how to choose the king of kings, in the end we decided to abort the project because, among other things, such things are a bit of a logistic nightmare. In particular what troubles me the most is that over time the new generations of players may no longer be tied to the common cultural background that ties the realms together, and simply do what they want. You may then go to war, but that's a kind of lame war cause you'd have to start everything from scratch.
In short: getting a 3 realm federation with vague cultural bounds to work together is going to be almost impossible. And if your empire does not work as an empire, all the fun of the project ends there. I'd say you need to work more on the cultural ties rather than on how to select the king of kings if I may give a suggestion.
Besides this, the idea of selecting he emperor with games is pretty cool. Even if to me it sounds like giving a very weak claim to the winner, and the Lurian area would definitely benefit from some reliable stability that will avoid people there killing themselves over and over again precluding any growth of influence outside their tiny region.
