You certainly have more knowledge of this than I do, but I've never had any luck trying to have 2 email addresses sync into one account. I believe you will wind up with 2 accounts, one on the old email address that will have all your projects and credits for the "retired" projects and the other with new stuff.

I run projects on a "junk" account until I get it to 1M. Then I change the email address to my "real" account and crunch a few WU under that email attachment. Then things get in sync and move to my good account.