Well, if I’m not mistaken (and I very well could be), the raw scan would have the different color layers separated already since it scans each frame’s red blue and green channel. You’d just have to take those different layers and recombine them more precisely.
Well, if colour filters and light were perfect, then yes.
However the real world isn’t as kind, so separating out a layer perfectly, with no crosstalk between the other layers is very difficult from a print. You can do it ‘well’, but doing it perfectly is a lot of fiddling around. Then you have the problem of when to do it in the chain, if you do it before dirt and scratch removal, then the dirt and scratches become harder to repair, if you do it after, the separations are harder to isolate, so it takes a bit of work.