We use Redmine in a corporate setting, so we have lots of registered users who may want to join the projects we host in Redmine. That's great, but I'd like the option of allowing them to add (and remove) themselves from a project instead of having to ask to be joined.

I think this would be a worthy option - not only for registered users to add themselves, but also to allow project members to remove themselves if they want.

So, I'd like to suggest a new role that is on by default for project members, off by default for non-project users, that allows that user to add or remove himself only from a project. This would be similar to the existing ManageMembers role.