I think you have done something similar to what the Doctor Who restoration team did to restore colour to some of the episodes whereby they took the luminance from a high quality monochrome source (the original 16 mm b&w telerecordings) and a VHS or Betamax colour palette only.
Of course they were working with a source that was made with a PAL colour video camera, but that separation is likely to still be there. It would be harder to do if the film was on BluRay but likely the colour would be great on that anyway.
I don't know what software you would need to take the chrominance of one source and luminance of another (as I'm sure it can be done digitally now), but back in the 90s the Doctor Who restoration team had D1 VCRs to work with. I will see if I can find the link about this.
here is the article I was talking about: http://www.purpleville.pwp.blueyonder.co.uk/rtwebsite/colouris.htm
and it came from: http://www.restoration-team.co.uk/
they just have an odd design of website on that site!
Of course as the Hobbit was film material and I don't know what version you are working with PAL or NTSC (although I assume that the VHS and DVD copies you have are the same type as each other) you could try working in 24fps as that is what the original film would have been, or 23.976 if you are using NTSC copies? Even if you are looking to have an NTSC copy at the end it might be better to edit from PAL DVD sources as that would be higher resolution but it wouldn't matter if the colour was from an NTSC VHS as that will actually have more colour information than PAL VHS anyway! Just remember to work in 24fps then output to what you want afterwards then it should be the highest quality you can get in both NTSC and or PAL!
In fact to keep the speed and the resolution higher upscale to 1080p 24 and add in NTSC DVD audio and it should be great!
I know it won't be actually HD quality, but 1080p 24 is the only way you can keep the resolution as high quality as the PAL transfer and keep the running speed the same as the film was at the cinema, whist also not having the 2:3 pulldown artifacts of NTSC.