It sounds neat, but feels like it might fall apart with higher-complexity formats. What does an embedded decoder for a PDF look like? I guess since they are tightly-coupled to the file bytes themselves, the author of the file gets to choose what formats make sense, but not all formats have a one-true-decode-step.
Despite the name seemingly implying otherwise, F3 is an alternative to columnar storage formats like Parquet; the goal is not to support every conceivable encoding of every file type such as a PDF. Think of the use cases being more like "What if you used a specialized compressor and need a custom block decompression algorithm" or "Decode internal format into Arrow output" or something like that.
