Consolidating Apple IDs and retaining purchases

I've been an Apple customer since 1986 with a Macintosh Plus computer. Being an early adopter, I was also an early subscriber to iTunes, the fledgling App Store, and then the problematic MobileMe, the precursor to iCloud. That's how I ended up with an @me.com email address, once MobileMe was shelved and iCloud was introduced, my @me.com address (with is equivalent to @mac.com and @iCloud.com) became my Apple ID for iCloud.

However, as an early adopter, my Apple ID for iTunes and the App Store was under a different email address (associated with an internet provider at the time, but to which I no longer have access -- before that account shut down, I initiated permanent forwarding to my @me.com address).

It has been a continuing hassle to have two Apple IDs, and really goes against the plan of having One Login for Everything. I have been told repeatedly there is no way and no plan to allow persons with this situation to be able to "combine" the two Apple IDs -- though I continue to make that request.

Reaching out to the community: If I wanted to use just my @me.com Apple ID for both, would I loose access to all the purchases I have made in iTunes (Music)? Would I need to repurchase the Apps made on the original App Store Apple ID? With music, there is way too much to re-purchase, but the song files are already in my "master" music folder on my Mac, which I use to load my iPhone and iPad -- would they continue to exist, but as purchased under a different Apple ID? Could I just add that original iTunes / App Store email as a Family member for Sharing?

Or does anyone have suggestions on this issue. This has been bugging me for about 20 years.

Thanks.