Closing this idea down because of two disadvantages:
shop-owners will get higher transaction costs while a cheaper (but slower) payment method is available
shop-customers might not enjoy this optimisation if they deliberately decided they did not want to use credit card again or wanted to use iDEAL, Bancontact etc so recurring payments use SEPA Direct Debit
I think we should also consider giving preference to creditcard mandates here, as this would solve the issue for customers that have an iDEAL/SEPA and creditcard mandate. Advantage: creditcard payments are faster, disadvantage: they are also more expensive. https://github.com/mollie/WooCommerce/blob/master/mollie-payments-for-woocommerce/includes/mollie/wc/gateway/abstractsubscription.php#L213-L229