I use to be able to merge by fiddling with the email addresses somehow, but for the life of me I can't remember what I was doing. Once the new changes were put in place I was unable to fool it anymore (this was between registrations and a memberships only).
I think a choice of "yes merge with existing record" after you enter an email already in use would be the easiest for me. That way a duplicate record could opened manually, updated with the correct email and moved to correspond with the proper person. Maybe a choice of move what? ie. events, transactions, membership, or "all" would be helpful too.
Sounds simple, but sure it isn't.
Thanks,
Jennifer Taylor
Ohio Wildlife Rehabilitators Association
www.owra.org