I think Unison paired with a strong graph database instead of the filesystem would be a powerful combo. It would very naturally represent the AST graph directly

I think Unison paired with a strong graph database instead of the filesystem would be a powerful combo. It would very naturally represent the AST graph directly and would benefit from graph db optimizations. The cost would be the need to invest a lot in new tooling: you'd want a graph db-based source control implementation that offers similar cryptographic certainty to git; you'd have trouble using existing tooling directly like text editors that expect files on disk; etc.