Brawlers Guild is...alas...from WoW. As someone who quit several years, and made the full jump to FF14 (Been on and off since ARR), I fully believe a form of Brawlers Guild would make a fantastic edition to FF14.

To summarize, Brawlers Guild is a single player arena. There are stands for people to watch your fight, and players queue up for fights. Each fight is essentially a solo boss fight, with the more you beat, the harder they get. If you beat them all, you get VIP access in a special area.

The whole thing is very simple, and maybe a bit niche, but it is content that is extremely fun to those people who find it enjoyable. A difficult challenge, along with watching others take it on. And a lot of times, players helping players figure out the fights, or how to improve their rotation/gear when needed.

It's a great community get together, past time, and enjoyable system. I've made friends in the Brawlers Guild that I still talk to this day. And I'd love to see something like Uldah's coliseum be turned into something similar.