Instead I'd create a SQL script that has the ALTER TABLE statements so that it can be checked, and that the update operation is run in a controlled manner.
in reply to Re: Automatically altering tables from different schema's
in thread Automatically altering tables from different schema's
I'm going for ease of use, so any changes would be "automatic" (with maybe the option of not deleting columns automatically). But there would be an API to get at the primitives, so that you can indeed do what you propose.