[@Ellri]
What you've described is why, if I brought my setting over to this site, unless I was working on a grander scale (which, like I said, I would probably just do on my own complete forum using the InvisionFree boards like I usually do since a site so large and public might not be appropriate), I'd likely see myself setting up an arc-based or event-based scenario.

Everything I'm saying here assumes I was willing to spoil enough information about my work to make character registration possible, which I'm currently not. If I was, however, people would be given a lot of information about the entire setting that they could read at their own discretion to gain insight, but the actual types of characters that would be possible to register would be somewhat determined by the current event or arc in question. That would prevent the role-plays from ultimately going nowhere.

This isn't set in stone, obviously, because I'm able to adapt the plot direction in a way that can cater to multiple character types. I'm all for characters taking their own directions and developing relationships, stories, and so on, but some sort of main narrative should usually be active in the background. I've got an overarching concept to my setting that allows a lot of very unexpected things to happen outside of the original plan without those ever really being able to prevent the key plot from eventually taking place, somewhere down the line.