Digital BW, The Print

Thanks to all for the interest and help.

I see a real problem in operating in 2 passes : the 'trick' appears obvious.

As for Imageprint, thinking it twice, if K LK and LLK show tones variations as it can be suspected I'll be left with BO (e.g. K only) and I'm not sure K dots will not be disturbing vs less visible color ones.

One thing that appears clear is that BW and color will be processed differently probably with 2 different profile.

In fact since greyscale neutrality is a subjectif concept (even disregarding paper issue), I start wondering if the easiest would not be to slightly tone the BW part. To optimise BW I'll be using a BW profil then turn it RVB, add a slight tone  amd mix this with the color-profiled color parts.

Am I right assuming a BW profil vs profiling all with a Col profil should get me a smoother, more neutral (unitone) and more contrasty greyscale. I'm tempted to think a BW profil will call for Ks more consistenly based on equal RVB values (even if a slight tint is added to the BW part ot hide undesirables casts) sent to the driver.