Your reply suggests you either couple everything or nothing. It’s more nuanced than that. Everything is a trade off. With that said,
it looks like this library will position itself in the center of your architecture — and I would be very hesitant
to do that.
Of course anyone should be hesitant to over-model the business domain in any part of the application including the database, but the entire reason of existence of the RDBMS is to maintain consistency with something, and if that something isn't the business domain, then what good does it do?
I don't know where over-modeling fits in the argument. Business logic in an isolated part of an application is likely to age better than something that is intertwined with a database or other external dependencies.
