Koen This would help immensely. Revolut for example allows this, even through in-app Apple Pay, which is nice. I know SEPA transfers are much cheaper for you so I understand you have to weigh the costs vs. the benefits. But it would be fine if you could restrict it to certain types of cards. Debit/Prepaid must be cheaper than Credit for example.
It would be good if you can check the possibility internally.
SOFORT is not a good choice unfortunately for Germany. You give your banking details and full access to your account to a third party who by their terms and conditions not only transfers the funds but also checks the transactions in your account. Very fishy (phishy?).