Who cares about logos...this is about practicality.

So you would give up all the features that the Canon FF has with Canon
glass in order to use Nikon glass that doesn't function? Remember that
the camera can't autofocus, no distance info to help meter, you must
manually adjust aperture, and no aperture ring on G lenses means you
can't stop down at all with them. That means lenses like the sweet
70-200 VR become nearly useless and really limits the usefulness of a
bunch of other lenses.

I understand the FF interest, but if that's what you want, then buy
the right tools for the job. In most of these scenarios, the problem
is simply the need for a wider lense. So for the Nikon it would be
cheaper to get a wider lense that does what you want than getting the
FF Canon body and adaptor along with all the headaches listed above.

Beyond the wide angle loss, cropped FOV sensors don't really give up
anything else to FF bodies. A 1.6x camera does just about everything
the FF does, with the right lenses.

For something like using a tilt-shift lense from Canon on a Nikon
body, I can see it because there is little or no option for the Nikon.
That's a specialized lense and the need could arise. But for the full
frame aspect, it doesn't make much practical sense.