Digital BW, The Print

Let's try this again...

How about 5 grays, plus CMY or whatever you choose to do the color
toning. The CMY would make it easy to keep a "normal" CMYK profile
workflow. I know, this is heresy, but it does allow for soft proof,
and color toning in Photoshop. Shouldn't be a problem to set up with
many of the better color RIPs.