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Provide options for primary and secondary payment options.  If the primary payment option fails multiple times, automatically use the secondary payment option.

You currently support the storage of multiple payment options so you are already halfway there.  You can allow the assigning of priority for each payment option.

Do you refer to the marketing default payment methods please? Our system set account balance as the priority and you could change that following the steps listed here:
https://www.dynadot.com/community/help/question/default-payment-settings