If it comes down to it, a dye bleach process may be the only way we can home brew color reversal materials from scratch. The simpler dyes are quite available and the coatings are simple. I hand coated and then machine coated a simple example at EK and then did a single layer coating here at home about 2 years ago. The example was posted here IIRC in a long ago and forgotten thread on a similar topic to this one.

Also, there have been several posts here where people have mixed up a dye bleach solution that works. I have, but have not checked it with the Ilfochrome material itself.