I'm excited about this and have some use cases already lined up but I'm continually worried about a grammar free-for-all and collisions as each extension author tries to modify the grammar. I'm hoping they already have something in place for that and I just haven't read about it yet. I'm concerned that you can load an extension and kind of mangle the interpretation of the syntax. Two author extensions could legitimately want conflicting parsers and there's no easy way to unload an extension in duckdb. Something like an explicit "GRAMMAR SQL" or "GRAMMAR GGSQL", etc would be nice.