Schweizer's reagent, or tetraamminediaquacopper dihydroxide, is used in the production of rayon. It does this by dissolving the cellulose which can be acidified to form strands of cellulose. I have had some success with this.
So, seeing as cellulose and nitrocellulose are rather similar, would it be able to dissolve it too? If not, why? The nitrocellulose would have to be able to survive the addition of acid, which should not be a problem since it is synthesized using sulfuric and nitric acids. So, as long as I use sulfuric acid it should work fine.
Something else that might affect it is how nitrated the cellulose is? Cellulose dinitrate and cellulose hexanitrate might act differently.
And now, assuming that it can dissolve it in some way, it could be extracted from that from celluloid plastic, like that found in ping pong (table tennis) balls?
So, by adding some ping pong ball to Schweizer's reagent, then letting it dissolve and adding it to a solution of sulfuric acid, the camphor in the celluloid would be left behind and you should end up with some sort of "nitro-rayon". This is a bit of a stretch, but to me seems feasible.
I will try this when I can, but for now I hope this is enough to prompt speculation.