Feature req. recurring CC line on invoice

We have an online system to accept credit cards, so we really don't want users to fill in credit card info on the stub of the invoice. So til now we've turned that off.

However, We often have customers asking if they can setup recurring billing. Our bank requires that we have their sig on file, but Customers don't ever seem to find the form and send it in. (they call)

So, I would love it if in the invoice setup you could add a swap type with 'recurring' (or something) button, and then perhaps instead of the "payment type" text we could have a line Like ()Check to authorize recurring payment

In fact, payment type is pretty self-evident anyway. If there's a check enclosed it's a check payment, right? Maybe that line could just be changed altogether... if nobody objects??