Ok, hear me out: what if we make something that takes a postgres database dir, tars it together and encodes it as a binary blob in SQLite?
We could have SQLite within postgres within sqlite within postgres! Is it practical or even slightly useful? Of course not - but it's SQL databases all the way down. Not that this is a good thing in itself.
Take it one step further, the table-oriented database(tm) , embed clickhouse, MongoDB, Redis and PostgreSQL to ensure you have more flexibility than anyone can utilize efficiently. The one database to rule them all.
We could have SQLite within postgres within sqlite within postgres! Is it practical or even slightly useful? Of course not - but it's SQL databases all the way down. Not that this is a good thing in itself.