I wonder how much of the RIC can be upgraded with the materials we have, keeping in mind that some of the footage common to the Donner Cut and the RIC is processed differently between the two (something I learned during a previous attempt many years ago).
I’d say a fair amount of it, picture wise anyway. Some stuff obviously has never made it to widescreen release, but a 4:3 composite of official sources mixed with VHS stuff would be a welcomed upgrade. All the deleted scenes on the bluray plus these new scenes is the bulk of it. There’s some alternate angles and a load of padding that would have to be from VHS/ RIC DVD. The audio would be the tricky bit. Scenes set to different music, and alternate line readings that are only available on the VHS. Without the original sources to go from, we would be stuck with the bitrate of the DVD of the RIC.