I might not understand everything the OP wants, but I've played with proftpd in the past. As I recall, it supported virtual users, bandwidth throttling, SQL integration, etc. *and* it had GUI's (gadmin comes to mind) available for people that wanted to manage it without spending a lot of time in the .conf files. If vsftpd and proftpd don't support what you need to do, please submit wishlist items to those projects. They may not have the specific feature you're looking for because the author is aware of an alternate way to accomplish the same thing.
