I miss the following operation:

   bytes->byte-vector : (list byte) -> byte-vector
     Return a newly allocated byte-vector whose elements
     are the same as the elements of the list

The function bytes->byte-vector could be defined as

   (define (bytes->byte-vector bytes)
      (apply byte-vector bytes))

but since apply copies the elements of bytes, this would
be inefficient.

--
Jens Axel Søgaard