Dear Philip,
Is there any way (perhaps through a command-line option to XeTeX) that one could obtain those most usedful diagnostics using XeTeX in "standard" mode
xetex -output-driver="xdvipdfmx -E" file.texor xetex -output-driver="xdvipdfmx -v -E" file.tex (verbose)
Default is "xdvipdfmx -q -E" (quiet). Best, Akira