How would you (any anyone else!) feel about using GitHub for this? I can create a repository of the current 'default' scenarios, which anyone could then fork, add their own scenarios, and submit a pull request so I could incorporate their submissions.
I have been looking at a more conventional 'file library', but I'm worried it would be difficult to avoid spammers and others trying to misuse this. Hopefully users don't see it, but most attempts to post in the forum are spam of some form!
Alternatively, if people want to email me with their scenarios, world models, ships etc., I'd be very happy to set up a file library where I would upload submissions myself.