Michael, what you want to know about is dye-mordanting techniques. There are ways to do exactly what you want; stain an image in proportion to its silver desnity. You can even bleach out the silver leaving only a dye-image. A stain like malachite green should work admirably, and you can easily get this from a wide array of sources.

It's different than dye transfer in that you won't be etching the film to make a relief matrix. I don't think this would work with commercially available b&w films. However, erikg is right in that a dichromate-bleach (like carbro) will harden the area surrounding the silver. In this way you could theoretically obtain a planographic matrix, which is not etched, but consists of tanned & untanned gelatin. The trick is, that the stain will go into the untanned areas, so that you be able to get what you're after. A relief matrix contains only tanned gelatin since you've etched/washed away all the untanned.

This planographic matrix was used to make dye-imbibition prints (dye-transfer) in the old Pinatype Process. The dyes are different though, and you have to use positives instead of negatives. Technicolor used the relief technique, which is akin to Kodak's classic "Dye Transfer" process.

If that sounds like what you're looking for, let me know and I'll try to dig up some resources.