Maybe I've solved this, or maybe it's a dumb idea - let me know. One of the things that seems to be a problem for a lot of people on the forums is being stuck with their long-established iTunes store email account and a newer @me/whatever email account.
Why couldn't you just use your new email account to set up new iTunes store and iTunes Match accounts, and then add the songs back up under the new account?
Why couldn't you just use your new email account to set up new iTunes store and iTunes Match accounts, and then add the songs back up under the new account?