Piping two gpg'ed keys to cryptsetup luksAddKey

This may be a feature request, or just a call for some bash scripting help:

I would like to add a (piped, gpg'ed) key to a luks partition that was 
originally formatted with a piped key from gpg:

Create the container
# gpg --decrypt --quiet 2>>/dev/null first_key.gpg | cryptsetup \
    luksFormat /dev/partition

So gpg will ask for my passphrase for my (usb random) key, and then pipe the 
decrypted output to cryptsetup, creating the container.

Now comes the question:  how to pipe in the original key and a new piped key 
at the same time, for the luksAddKey action.

I have tried unsuccessfully to use the --key-file=- option and some bash 
constructs like (subshells) and {code blocks} along with pipes.  The best I 
have been able to do is get the new key in, but with a <cr> added or some 
other mangling.  That doesn't work, when later trying to luksOpen the 
container with the new key.

To clarify further, I don't want to use an intermediate or temporary cleartext 
key, or UUencode either of the random gpg keys.  I also don't want to take 
the key apart and write it to a temporary file.

If we can't find a way to do this, I will be happy to help with a patch.  I am 
not a good enough coder to solve this on my own, yet.  I do think there is a 
need for this, please offer any suggestions.  Thanks!

Mick Reed