It would be really helpful to have an option to easily consolidate any unpaid or past due invoices into one so the client can make a lump sum payment, rather than individual invoices that need to be paid one by one. I've had clients report they are prevented from paying multiple invoices (generally more than 2) at one time because of some arbitrary time limit between payments, I've had it happen as an administrator too. It says something like, "Try again in 5 minutes." A consolidated invoice with one payment could make this easier on me and my clients--hello, ADHD.

Moreover, being able to schedule a payment to run automatically on these consolidated invoices would be a huge time-saver. For example, if "Invoice is not marked as paid" by "X date", then "Run default credit card on file" for "Y amount" at "Z time".