We're building something that partially overlaps with this at Splitgraph [0] (co-founder here). Instead of bitemporal tables, we're using columnar storage (cstore_fdw) + delta compression as a storage backend and support Git-like operations (commit, checkout, etc...). We also let you build datasets with a Dockerfile-like language as well as share them with other Splitgraph peers or the public Splitgraph catalog.
[0] https://www.splitgraph.com/docs/getting-started/introduction