Years ago I remember this website had something pretty much as you describe. I guess the best way to describe it was like the arena but with talking. They were never really my thing due to the innate lack of direction but it always seemed like a popular place for people to exhibit their characters. I remember this website also tried to set up a PW a couple of times which in a way was similar to the Inn concept except with worlds. That was awesome for the month where it worked, you had like six plots going on in one setting and multiple settings. It was just too much to run though and inevitably collapsed. The Inn thing sounds totally doable though.