I had a bit of a go at the new srfi-60 for the cvs head (below).
There's only a half dozen functions not already in the core.

`bit-count' clashes, in srfi-60 it's an alias for logcount but in the
core it's for bit vectors.  I'm not sure what to do with that.  It
should be exported, but there'd be a choice between letting the usual
"override" warning come out, or perhaps suppress that and make the new
function accept the args of both the core and srfi-60.