As I understand it, soft proofing allow one to see (more or less) what a print will look like on the paper, and according to Schewe you then put on an additional curve to bring the view of the print back to close to what you wanted in the first place.
The question is - why can't the program do most of this for you? - after all, it has the original image, and it has (via the soft proof) what the printer will produce, so can't it generate a curve to "fix" the result.
I suspect it's not that simple, but it it should be possible.
In Lightroom, maybe the "print curve" could be a separate function some how attached to the paper profile.
PS That title was meant to be " A question for all you printing experts"
Software can perform mathematical operations on pixels. It can't tell what a print should look like, because that's a subjective aesthetic determination. To my eye soft-proofing in Photoshop provides an exaggerated view of the loss of gamut and contrast you get in the transition from screen to paper. This can give you a rough idea of what kind of contrast and color moves might bring you closer to the screen appearance.
The best practical discussion of proofing and adjustment I've found is at www.johnpaulcaponigro.com
where the artist provides a series of downloadable PDF's on the subject. Good stuff.