Frog: Are you asking if anyone actually does this and their experiences with it?
I did at one point in time try it out - but weeding out all the mixes that had white pigment in them was a pain/time consuming. Worth it for huge jobs, or if you have lots of down time to play.
You also want to pay attention to how much color is going into the mix - depending on just how "black" you want the ink to look.
Some are fine and dandy with it being an "inky" black - others want a total lack of color "black".
Either way, I have always recommended adding junk ink of choice 25%-40% to a finished black - or into an in house mix of black ink with a 10% black pigment load to cover up the colors being added.
I would then add ink modifiers to create the print qualities you want.
I have talked about a first down chromatic black I made for a job involving multiple flashes. I used about about 2% black pigment into my chromatic mix of (8% ish) red/green/blue... juuuust enough to look closer to black but not go up in smoke under the quartz flashes.
Hope this answered your question