I think I'd agree MadDog. In fact a part of the reason I was so eager to post the little bit of info re the galaxy we call the Milky Way was to show just how big space is.
I mean there is more galaxay above
AND below the middle of the disc out here than the Imperium is across. I think. Its a guess. Hmm let's see 1,000 parsecs thick and the Imperium is about 5 sectors across times 4 subsectors per times 10 parsecs per is about 200 parsecs. OK make that double, so its thicker than the whole of the bulk of charted space, both above and below the plane. Sol is I think a little below the plane iirc but that's beside the point.
Edit: And my memory fails me again, we are actually just above the equatorial disc, a mere 20 light years. Gotta love the net for quick google facts, when you can trust the source
The late Carl Sagan really put it in perspective by noting that we are one mundane world orbiting one unremarkable star in a galxay of billions of stars in a universe of billions of galaxys, not his words but the general idea.
So if you want to tackle a 'realistic' 3D galaxy you're going to need to change the Imperium significantly. Like only a few star systems are worth putting a mark on the map, and the average jump will have to be more on the order of J6 with drives going up to J36. Even then to traverse the depth of the outer spiral arm in our neighbourhood would require about a year with good speed. And forget about making a trip to the Andromeda galaxy in your lifetime, even if you could find fuel to do it.
I'm rambling, let me finish with "Space is big. Really big. You wouldn't believe how vastly hugely mind-bogglingly big it is." and advise that if you really think there's nothing left to explore, all the frontiers have been conqured, and everywhere you go there's somebody else's bootprints, then you really aren't looking. True today on Earth, even in your own little part of it in all likelyhood, barring you're trapped in a concrete jungle. Hmm still rambling, somebody just hit the add reply button for me alre...