> And what if we could deploy modifications to that datatype (ex. adding a database field) in the same uniform way we do all other minor variations to a datatype?

If you mean propagating changes to a schema across all layers of the stack, that may not necessarily be a good idea. In my experience we want to keep the datatype definitions at different layers somewhat independent of each other, to allow evolving separately. For example, the database table could have a `more JSON` column to allow adding data that was not foreseen in the original table design; but the application's datatype would decode that JSON into specific fields to show the user perhaps.