I would buy an Autochrome-type film for the effect, and I would buy a Dufay-type film to use if normal color process film became unavailable. Dufay film was available in 120, so I'm sure that nothing will change for that process.

Since Ilfochrome will no longer be made, that would mean a replacement paper would have to be developed. The other alternative would be a balance for RA-4.

A prototype Dufay might be constructed using the Efke Aura. I would try printing a screen on the back using pigment ink, and then see if that survived normal processing. Their normal IR seems to have a decent back side for retouching, and it at least accepts marker ink quite easily.