Im not computer genius by any stretch, but wouldn't it possible to see the kext or issue at hand if you compared the last known iTunes version working and the current ones and see what differences in code or kexts are available? That would help narrrow down the culprit.
Then maybe create a hack/modified version of the latest itunes with the necessary file to make itunes movies work incorporated into the latest itunes?
Unfortuantely all this takes time so I can understand peoples reluctance to find the problem. That and not many people are programmers to figure it out.
For example, lets say itunes have 4 files and theres A and B versions with C the modified version. (for easy explanation sake), Itunes C V1 contains 3/4 files of version A and other from B. Dosent work. Next V2 will contain 2 files from A, 2 from B and test. Wont work.
Its a bit of a probability game but is this one approach?