Sounds like a whole lot of effort for the same thing. Shooting on film i understand. Doing the editing and post work on film seems unnecessarily complicated, difficult, and expensive for a final result that would be nearly indistinguishable (again not talking about doing the initial shooting on film). Especially considering almost any place that would show your film would just show it digitally anyway. And you could still make prints of it anyway.
But then again I’m not speaking from a film enthusiasts perspective.
Pretty much what Dek said. If you do it that way, you’re limited to the resolution of your digital intermediate, and it would be much more difficult to go back and find all the negative to rescan if it wasn’t already conformed to the locked picture edit if you wanted to get it in higher resolution.
This is why a lot of 4K UHD releases are upscaled 2K - because their digital intermediate was 2K and it’s too expensive to find all the right takes from the negative and rescan them at 4K. That, and most CGI is done at 2K even today, so effects-heavy movies will probably always be upscaled from 2K.