The setting could give some interesting stories, but what exactly would you want to do with it? When would you set it? Given that it's the setting of an MMO, there's so much that you could do that's fun, but just having the world doesn't mean much.

Like, a heist RPG about robbing, say, Varrock's bank? Stealing shit from the Kharidian pyramids? The God Wars? Wilderness exploratory groups? Surviving the plague in Ardougne?

It really boils down to what you wanna do.