Proposal

Wow, making functions that only return a simple request is a bit extreme in my opinion. I understand the need for separate functions where there is some logic involved so it can be reused by the web API, but not when it's only a single-line request, or just a database insert.
If our need is to be independant from Flask because we don't know if it's going to be there in two years, fine, let's take precautions against that. But I don't see us writing code indépendant from Flask AND SQLAlchemy without it looking like a spaghetti plate.
That's what we tried to do in KittyStore, and two years after I can testify how it's been a real mess/pain to deal with. Let's have a veeeery narrow window of where there are long-term risks, and work around them. I agree Flask's in it, it's new and shiny and the web changes fast. But I don't agree SQLAlchemy is in that window.