If I order a retina iMac with 3 TB fusion, and later decide I want to put a 512/1 TB SSD in it with TB external storage, is that possible without going all Macgyver and voiding my warranty?
ifixit have done a tear-down which suggests it can be replaced, but it involves cutting the double sided tape and taking the screen out completely, then re-taping. I'm guessing that's more than most people would be comfortable with, and I doubt your warranty would like it either.