This makes me so happy - I was going to do this in the same way - use theatrical Blu-Ray and only fill in EE shots from the EE BD with EE DVD chroma overlayed - I even started working on it but never could find the time to finish it, so I’m really glad someone has done this and even went above and beyond.
The only thing I probably would have done differently would be to replace some of the worst looking scenes in the theatrical with CCd EE - the theatrical BD looks really nice 95% of the time but there are a couple of scenes where the DNR was applied much heavier than the rest (off the top of my head, it was the scenes where Gandalf talks to Bilbo and then Frodo inside Bag End and then Gandalf’s confrontation with Saruman). Since they are theatrical scenes, the theatrical BDs chroma could be overlayed for those instead of the DVD. Might be something to think about for the next version. But even as it is now, it’s far better than anything we have from official sources 😃