This page is part of the web mail archives of SRFI 66 from before July 7th, 2015. The new archives for SRFI 66 contain all messages, not just those from before July 7th, 2015.
I don't think it would be a good idea to include BYTE-VECTOR-FILL!, BYTE-VECTOR-COPY, & BYTE-VECTOR-SUBSEQUENCE (which might be better named BYTE-SUBVECTOR) in the initial proposal; the first has been deemed not very useful, and the latter two are both trivially built atop BYTE-VECTOR-COPY!. My suggestion was only that the bare, minimal interface be augmented by an important primitive; adding library functionality to the base interface is probably not a good idea.