Is it okay if I provide a build option so pax will not install a "bin/tar"
but will install "bin/pax-as-tar"?

This will be:

Patch pax's file_subs.c, options.c, and options.h to add a new
NM_PAX_AS_TAR to be like "pax-as-tar" that does the same as NM_TAR. And
then install a symlink (or hardlink) with same name to pax.

This same option would be used for pkg_install too so it would use
"pax-as-tar" instead of tar.

This will be an option. It will default to be same as it is now for you
all.

Why do I want to do this? Because I don't like pax and gtar-base
installing to same file name when using GNU_PROGRAM_PREFIX= as nothing.
Then pkg_install breaks because GNU tar is missing --fast-read option.

   Jeremy C. Reed
   http://bsd.reedmedia.net/

p.s. Any volunteers to provide a --fast-read option to official GNU tar
code?