Collaborative multiuser site

Hello,

I’m interested in setting up a WordPress site for our community committee members that we can collaborate on. It should be a single WordPress site with multiple users.

To give you a flavour of what we would like to achieve, I have listed key features that we would like for each member:

login and create their own profile.
have the same view of the website (except the administrator)
write posts
plot markers on a map
each marker will have a specific type e.g. Pub
add details to these markers through a form (different form for each marker type)
All markers of the same type will be added to a layer (table in a database I guess)
Once a specific layer has been created by a member, other members will be able to add to it.
Finally, all layers will be visible on our homepage map where non-members can see them

Does anyone know whether this sort of thing already exists? Alternatively, could someone explain how this might be achieved with plugins?

Would it be best to build this site for 1 user with a map and the above functionality and then subsequently add a multi-user feature. OR would I need to do it the other way round?

Your advice is greatly appreciated