Hi Martin,
Sorry for very late reply.
There is no need for mock-up really. Read this lines if you've never tried assigning an ICC profile to a document:
"...First at least one CMYK profile needs to be added to the document being worked on. That can be accessed in the GUI through the "Color Management" tab on the document properties dialog. Once at least one profile has been added, the color pickers in the Fill & Stroke dialog can be used to pick colors in that colorspace via specifying the ICC profile." [1]
What annoys me is that even if you have only one ICC profile attached to a doc, you still need to manually select it from a drop-down combo of CMS tab (Fill&Straoke dialog). Can Inkscape automatically pick it for me?
Regards,
Vlada