There are several vendors who do this, for instance 1Password and the Omni Group both do. You have an in-app purchase option that is unlocked by a previous receipt. The challenge is that Apple does not provide tools to help or guidance. They do indeed think e.g. requiring users to buy an upgrade to keep the app working on a new annual iOS version or macOS version is a bad model for users.

Panic even had an upgrade for MAS users when they released their new version of the now defunct Coda outside the MAS (for sandboxing reasons).