After a mildly ridiculous amount of effort I made a bootable-usb key.

I then layered a bash script on top of a perl script on top of gpg. What could possibly go wrong?

 #!/bin/bash

 infile=$1

 keys=$(gpg --with-colons  $infile | sed -n 's/^pub//p' | cut -f5 -d: )

 gpg --homedir $HOME/.caff/gnupghome --import $infile

 caff -R -m no "${keys[*]}"

 today=$(date +"%Y-%m-%d")
 output="$(pwd)/keys-$today.tar"
 for key in ${keys[*]}; do
     (cd $HOME/.caff/keys/;   tar rvf "$output" $today/$key.mail*)
 done

The idea is that keys are exported to files on a networked host, the files are processed on an offline host, and the resulting tarball of mail messages sneakernetted back to the connected host.