Sounds like an interesting project. Granted, I’m not a web-developer, but I can think of two ways if you were going to try for an “out-of-the-box” solution that an Author might sell here on Market.
Solution 1: A blog with multiple contributors.
The first solution would be to use a regular publishing/ blogging theme, for example:
Assuming your guests are people you know (and not everyday visitors to the website), you could assign them a type of custom "story publishing role"using a permission/ role creator plugin like this one:
This would let you grant limited access to the blog, and have different contributors to your publishing platform. You could “lock” the pages that you don’t want them to change, and give them access to the ones where they can publish. Their “stories” would be filed away like a standard blog.
Most blogs will let you profile the contributor, the Envato Blog for example:
Solution 2: Create a basic forum.
The other option would be that you literally create a forum (like this one) on your website. That way people can create accounts, explore posts from other users and even interact with each other.
Again, you can buy a theme, or you can buy a plugin (like this one) to add to a theme.
Happy to be corrected if anyone else has any better ideas?