My dream is, instead of separating data storage, state machines, valid state constraints, and the logic that transitions between valid states, we can actually unify these into some kernel of app state. Honestly, Postgres already has a lot of these capabilities, but I don’t see an obvious story on the app or product level, providing provably correct sets of states that apps can transition between, and which they can automatically expose to clients in informative ways (this user can like this post, but not edit). It looks colored Petri net shaped to me, but I don’t yet see a simple app state paradigm in the same way that the database has obvious successful boundaries.
Version control might not be a big deal if you are all-in on the database.
Stored procedures are easiest to version by simply defining multiple variants and then incrementally moving the callers in the direction you want. The durability comes from (hopefully) your backups. Point-in-time-recovery is often easier for the business to reason about than a git repository.
Having worked for a business that made a serious go of running everything out of stored procedures, I have to say that lack of version control was a huge problem and effectively limited all development to a single person who held all the rules in their head.
This is essentially what we do. All of our stored procedures, views, etc are kept in *_api schemas. Those schemas just get fully dropped and reinstalled whenever we migrate. It works really well, and has basically zero cognitive load overhead for developers.