1.In order for this to work, you need to make all your users set a new unique username from userdashboard.
2.You need to create as many subdomains as there are users(hard to do....)
3. If you would swich to "domain.com/username"
a)you need to make shure that no category has a name that is identical with some username or "contact", so you will have to complete in admin these banned words.
b) you can redirect via htaccess all
/user/profile/* to /*
