Wow... that's an expensive solution (depending on how much stuff you had purchased through an itunes account with non-apple email).
I've found that my two apple IDs live side-by-side with no problems. One is for icloud (formerly idisk and mobileme) services and the other for itunes purchases (which is linked to another email). Perhaps one reason that Apple has no intention of creating a way to merge apple IDs is because for the vast majority it won't cause a problem.
Having said that, I can see it would be a PITA for people who had purchased media and apps through 2 or more apple IDs.