I was thinking of using it with Duckdb as well but seems it would be of limited benefit. Parquet objects are in MBs, so they would be streamed directly from S3. With raw parquet objects, it might help with S3 listing if you have a lot of them (shave off a couple of seconds from the query). If you are already on Ducklake, Duckdb will use that for getting the list of relevant objects anyway.
Maybe the OP is thinking of reading/writing to DuckDB native format files. Those require filesystem semantics for writing. Unfortunately, even NFS or SMB are not sufficiently FS-like for DuckDB.
Parquet is static append only, so DuckDB has no problems with those living on S3.
Pre-compaction the recent data can be in small files, and the delete markers will also be in small files. This will bring down fetch times, while ducklake may have many of the larger blocks in memory or disk cache already.
Reading block headers for filtering is lots of small ranges, this could speed it up by 10x.
For files up to 100kB of size, this should effectively be really close to the same price as S3 when writing (didn't check reading so much, but the writes/PUT is always much more expensive than read/GET)
Would be really useful pre-compaction and to deal with small files issue without latency penalties