Let’s say Guilds exist on ToS. Every Guild can have a base, like on a floating island or something that can make it move to places. Every base can have a single Castle. Castles can be designed and improved by using materials to build and upgrade walls, fortification, castle height, cannons, towers, bridges, guards and etc.
Once a guild have a castle on it’s base, a guild can go to war against other guilds with the same level castle as they are. Bases move and go front to front, bridges are laid down. Objectives are set. And everyone can fight to destroy the core of the castle. Wars have a timed limit. Sabotage, Attrition, Raiding, Siege, Direct and indirect attacks and etc. are possible moves to win the war.
Characters that are participating the battle have limited number of lives. They can go fly through air, by riding a griffin or a flying device, and even air battles exist. Guards can be deployed and rallied.
Rewards and ranking exist between guilds making it more competitive.
This is just a concept of mine. What would you think if they applied something like this in a Guild war? Would you like it or not?