I am also looking for a solution to this topic. I searched all the different forums and Websites without any success.
Here is what I have: A Blog for an NGO running on regular Wordpress with more than 100 Authors. Registration is open and every new user is checked "by Hand" if he/she is related to the NGO and then gets either kicked out again or "upgraded" to Author. In addition, Authors rececive a user-role via a plugin in order to be able to visit an internal area of the blog.
Now, this is what I would like to have: WPMU with the above mentioned Blog as the Main Blog. Registration to the Main Blog should be still open and the "hand-picked" Auhors (the existing Authors and the Authors in the future) should be able to create a Blog themselves without emailing the Site-Admin.
With the Options build into WPMU this is not possible. You can either
-disable everything (registration and blog creation)
-enable everything
-enable only registration (then there is no blog-creation for the Authors)
-enable blog-creation only for logged-in users (then there is no registration)
With andrea_r 's plugin it is possible to force people to registration first, but then all the new users can also create a blog without being checked on and upgraded to Authors.
The problem is, that all this is handled by the wp-signup.php. It would be nice to have the ability to seperate the registration from the blog-creation. Or to figure out a workaround.
With the Plugin "Invitation Code Checker" it might be possible. You can leave the registration + blog-creation open and put an Invite in the area only vissible to Authors (the internal area of the blog). But only if it is possible to use the invite code seperatly with the registration and the blog-creation. Otherwise there is no registration, because the invitation-code is invisible to the "future-users".
And now my Question (sorry for the extensive intro):
How can you use the "signup_extra_fields" in the wp-signup.php only for new blog-creations? In combination with andrea_r's user_signup_plugin it might be the solution.
Or is it all a lot more obvious and easy? Maybe I'm getting blind staring at code all day.... .
I really fell in love with WP an recently also with WPMU. Does anyone have any ideas? I would really appreciate it.
Thank you very much!