Thinking about it I'm a particle rather than astro person so I'm actually almost as in the dark about this as the rest of you. However I do share an office with people working on the Sloan Digital Sky Survey - probably the largest space map ever made - so I might well tap them for ideas.

Just one note on your thoughts on units - light years are a sensible measure of distance as light is the only thing with a constant speed in the universe so measuring distances by the time that light takes to travel is a sensible choice. Obviously the concept of 'year' is the thing that would change.