I can see it would be useful perhaps to have two shapes then, i.e
keep them separate. One for 'safe emissive conditions', and one for
typical reflective conditions, assuming D50 white point with optimal
lighting, perhaps as you might find in a gallery [and not the average
home loungeroom].
For some purposes, yes. The emissive one is still pretty arbitrary
however (how much light to you assume it can generate at an individual
wavelength, compared to the white point ?), and even the reflective
one has a degree of arbitrariness, in the choice of illuminant.
An associated factor (which is largely being overlooked in
all this I think), is that the color gamut of an emissive
device can be manipulated by the choice of white point.
Using display calibration to set maximum brightness defeats
this idea, and the normal ICC way of storing relative colorimetric
information also works against it, but if the
maximum brightness was set in the profile (and
this might be something as simple as setting a
white point below the level of the maximum output,
depending on how the profile was subsequently used),
the effective gamut of a display can be boosted
considerably in the area of bright saturated colors.
I'm not sure this would help much in making a display
encompass more of a printing gamut (since printers tend to
be large in the darker saturated colors area), but
it could help (particularly when modern LCD monitors have
brightness to burn.)