I have guests going to my web site attempting to make a payment, but there's no built-in method to make a payment for existing bookings on hosted sites. Guests typically make a payment at the time of booking, then weeks/months later the guest want to make monthly/periodic payments, while other guests want to pay off their balance in full. The hosted web site doesn't offer a way (that I'm aware of) for a guest to go to the web site, type in their last name & booking number, and make a payment.
This could be a simple page with a form prompting for last name and booking number, which would generate the payment link and take them to that page. I don't know how that link is generated to make this page myself.
As a workaround, I could send out the payment request email more frequently via trigger, although this would generate more emails to all guests.
Let me know if there's a similar feature request already made, I searched and didn't see it.
I think this ties in with the requested "guest portal"....