Inventing a new language and a new query engine and a new storage engine at the same time, competitive with the state of the art, is maybe just too much to be feasible.
There were multiple optimizing compilers which can do a lot of these asks, allowing composable queries that return nested types, but produce SQL queries. I think the pathfinder compiler had the most real-world use, it was meant to efficiently mix SQL and xquery to query SQL+XML documents stored in postgres. It had a c# linq frontend, but also fairly hefty compile times.
There were multiple optimizing compilers which can do a lot of these asks, allowing composable queries that return nested types, but produce SQL queries. I think the pathfinder compiler had the most real-world use, it was meant to efficiently mix SQL and xquery to query SQL+XML documents stored in postgres. It had a c# linq frontend, but also fairly hefty compile times.