That's true, it would solve some of these problems. I do think the ultimate solution needs an awareness of both the diff and the migration plan though, to be ab

That's true, it would solve some of these problems. I do think the ultimate solution needs an awareness of both the diff and the migration plan though, to be able to test for things like whether changes can be made without downtime in a particular order. Unfortunately I suspect that the tool _also_ needs runtime instrumentation of the database in some cases to understand behaviour enough to address all of these concerns.