This is awesome. I run a team that uses software I produce and i have a rule that i can’t deliver breaking changes, and i cant force migrations. I can do the migration myself, or i have to emulate the old behavior next to the new. It makes you think really hard about releasing new APIs. I wish this was standard practice.
Sounds like an easy workaround would be versioned APIs then. Missing that, it sounds like the API will forever be stuck, or add-only, creating a mess. That is, if it is not already very stable.