What I’d like to see, for compliance with the GDPR without trashing data, would be for an unsubscription request to replace the email address with a one-way hash of the email address, set all attributes to a blank or default value, and blacklist that subscriber record. This way the records would remain but we would no longer have the person’s actual data. This could also be done with a unique replacement value (e.g., UUID), but a one-way hash could be used (with extra processing, of course) to prevent accidentally re-importing a blacklisted address.
Simply deleting data leaves us open to re-importing the same data against the person’s wishes, either by accident or through someone maliciously using our list to harass someone else.
Of course it’s easy to say what I want without writing any code. If I could, I would try to contribute this myself. That’s not feasible for me to do at the moment, unfortunately.