block renewal for accounts with outstanding invoices
If account has outstanding invoices, the software will not allow account to be renewed (generate renewal invoice) until paid in full.
automatically add non paid manual invoices to as line items to member renewal invoice
A member should not be able to renew without paying the manual invoices that are not paid
Move to a pay as you go process, and you will never have outstanding invoices. The only outstanding invoice you should have is for membership, and if they don't pay for that, then automatically archive them.