Blogfarm registration form

The standard registration form for blogfarm has groups, blog url and site title as required fields.
I’d like a person to be able to register first. When they register they would be directed to login welcome page where they have a choice of either joining a group or creating their own group or just creating their own blog. When they click on Join a Group, they will go to the homepage of that group.
If they choose to create their own blog, they will be directed to their own page. (a group will have different levels/options to create their own webpages).
Is this possible ? or partly possible? or can someone point me to relevant instructions ?
Thanks