I appreciate this effort. But isn't integrating Stripe fairly easy with Stripe Connect button (https://stripe.com/connect) without any effort on backend, or even integrating any backend code?
That said, there's not much to my app. Just some rails routes, a form, and Stripe Checkout on the client side. But it gets the job done.
Connect is for marketplaces and does some amazing things to make 3 party payments substantially less painful.
Checkout is for 2 party payments and does some amazing things to make getting credit cards and storing them in a secure vault substantially less painful.
However, neither solution is drop-in zero-code.
Stripe focuses on removing friction at the hard parts of the problem so you can build machines that do payments, Paypal focuses on payments that require no effort on the backend.