Extreme parallax
-smile-
Imagine the time-matching headaches processing signals light-years apart... though I suppose proper motion is slow enough that a precise match won't matter.
What I'd like to see is probably achievable a lot sooner: a simulated 3D model (R.A., dec, and distance) that can be flown through, and rotated and zoomed from any point. Say, to a radius of 50 ly for Version 1.0. I'd love to look back toward Sol from other vantages, and to see how, or even if, the constellations change.
JPL's solar sytem simulator is as close as I've found to attaining other POVs. It was fun to use it as a tool, too: confirming (in my own mind, at least) the first photo one of the MERs took of Earth and Luna in Mars' sky.