You use several API, attach one provider per customer to divide the risks. When one provider bails out, you onboard new customers and new payment on the other p

You use several API, attach one provider per customer to divide the risks. When one provider bails out, you onboard new customers and new payment on the other payment provider. Then you only loose the recurring payments on the lost provider that are on hold, and you are not dying, so you can resolve that problem using a lawyer. This is crisis management, not technical perfection that you need for those situations.