NavList:

I know you're asking lightheartedly, but, because the OCD is kicking in, I'll give the best answer I can.

I think the answer is "whichever you would like".  The aircraft's INS maintains an orientation estimate, so any point on the aircraft can be solved for position (in a desired frame).  So if the ITRF position of the phase center of the GNSS antenna, on top of the aircraft, is known, and the orientation of the aircraft is known, then every other point on the aircraft now has a position.

Normally one would only really care about certain key points on the aircraft, such as antenna phase centers and camera entrance pupils (same thing really).

ObNavList:  every ship should have an INS.  That way you can use local landmarks ("shipmarks") on the ship itself as a horizon reference, provided you are very, very quick with the sextant and timestamp.  :-) :-)

Cheers,

Peter