I see what you're driving at now.
That pic I posted is definitely built up on, or I should say with, white. The different thing about DC though is you can print white say overtop black and that area of overlap is grey, do it the other way around and you get the same basic thing although the grey will be darker. So overprinting white last may not be as much of a registration nightmare as it sounds, if it's off reg a little the CMYK colors will still get some information through. If the seps had complete and even coverage of all colors (there's a term for this, can't think of it) there should be no problem with any shirt showing through.
Great discussion! If this process could be mastered you could WOW print full color on 6 head press CMYK+White+bump color. That's what we've been driving at here, but with sim process instead and while prints are coming out really well, there's much to be done on the production side. We don't really get enough opportunity in the work we get to go all out in developing our full color printing, I'd like to though.
