I would report only when a customer uses Stripe as a payment platform.

Stripe does have an API to delete credit card, https://stripe.com/docs/api#delete_card ; however, the Developer Portal doesn't have a button to delete an existing credit card. This is apparent in a Rails partial: https://github.com/3scale/system/blob/73c83d47cc01775b0f8a18ef9b57d9629fbb370a/app/views/payment_gateways/_stripe.html.erb .

Ideally, each developer should delete his/her credit card on the Developer portal. They may become a no live or free plan user. Nevertheless, the developers are unable to delete their credit card under current implementation.