A roleplay of possibly infinite possibilities, but also structured? Is such a thing possible? Indeed.
Looking at my name you may see I do not have many posts, but I have been very active on Discord under the name AJ. Here is my offer.
Pandemonium. A group name for both a single dimension and a dimensional cluster. Many, many years ago the realm of Xaelinoc expanded into a realm named Pandemonium, and the ruler of both planes became very, very powerful. He took the name of God-King. Santioc Demonous, God-King, had big plans. He planned to conquer the neighboring dimensions. After the Great War, which he did so, he unified them all under his crown dimension, Pandemonium. Here we are today. We have five dimensions to offer. Alissa, the plane of the humans, named after their Goddess. Santioc, the realm of the high class angels. Xaelinoc, ruled by the Heir of the God-King, realm of the demons. Bael'Kath, the realm of the horrors, ever changing. Olv'Thrane, the realm of the World Tree, and the eternal guardian Elves. All swear servitude to Xaelinoc, and more importantly Pandemonium, but no such vow is to each other. These realms compete with each other, each trying to be stronger than the other, and sometimes have outright invasions. Each realm is under the whim of their duke, bound by law to not attack each other directly, but they do attack each other's realms with their armys, a loop hole that exists as long as they don't lead them themselves. You can choose to serve one of the four Dukes in their efforts to be the top, or choose to serve the Heir himself and play the diplomatic game in the Royal Court.
There are many choices in the Multi-Verse. Where lies your dream part of Pandemonium?
Afternote: There is a lot more information on the rp source, which is on Discord. Talk to me in the Discord server for the link.