Interesting prompt to world pipeline. I wonder if there can be more style applied than just the "MMO cartoony" style? Like medieval Witcher or realistic Cyberpunk buildings?
In modern polished games, the art team spends a lot of time tweaking things to make sure it looks great and coherent. Most people are not willing to have their agent run for a month to do this work. I don't know if it's been tried yet but I would be really interested to see the result.