The models live in version control. It's that simple.
If your data structure is changing so often in such a way that you need to keep a history, then I'm afraid you have some fundamental problems that no amount of tooling or process can solve. You will not be able to scale your development efforts with this type of constantly changing data model, even with a migration library.
If these are truly problems that you or your team has, then you should hire someone to help you organize your application, data, and workflow in a more effective manner.
If your data structure is changing so often in such a way that you need to keep a history, then I'm afraid you have some fundamental problems that no amount of tooling or process can solve. You will not be able to scale your development efforts with this type of constantly changing data model, even with a migration library.
If these are truly problems that you or your team has, then you should hire someone to help you organize your application, data, and workflow in a more effective manner.