I think this idea is a dead end. The Git model is already good for decently large and long-running projects like Linux (although not giant corporation monorepos

I think this idea is a dead end. The Git model is already good for decently large and long-running projects like Linux (although not giant corporation monorepos). So the version control problem is solved both for all past and future languages which are textual. But with an AST system you make the storage itself much more opinionated. Java and C ASTs are different, surely? So then the same storage can’t be used directly. I have also thought that these ideas that you bring up could be built on top of Git. So Git solves the primitive task of storing code in a completely unopiniated way—doesn’t matter if “the tests pass” or whatever. Then what you propose lies on top of that primitiveness.