What I would like is to have the game work essentially like it already does in terms of using the map in FO3 to travel long distance. One change though, that of having offset spawn points for the PC.
These would be used to 'fade in' from map travel. Imagine the PC chooses a town on the Pip, and the game pulls back into TPP (like 90' back), and you see the PC running off in the direction the town... In the interim, the map progress is shown (much like how the rest of the series does it). Upon arrival the camera is still TPP and the PC is jogging (or limping) towards the entrance to the town ~where upon the player resumes control; (The PC was moving away from the offset spawn point some ways back from the entrance to the town).
*http://www.youtube.com/watch?v=XbigblL3wbU.
The second part of what I'd like to see, is towns and settlements a long way apart, to where travel like the aforementioned above is the practical preference of most players ~but.... the neat part [IMO] could be to allow the PC to actually walk the whole way in real time if they really wanted to. Arcanum worked this way, as I understand it, the player could in fact walk the PC from the East to West coast; (and it supposedly would take two days in RL to do it).
If they designed a streaming wasteland that was a jumble of varried geometry (tiles) that randomly loaded in as you walked, and occasionally loaded in an area with stuff to investigate ~like an old steel mill, a Gas station, or bombed out town for instance
These areas would not usually be much more than landscaping, but some could be, and others could be full blown encounters with NPCs ~stuff you'd likely miss if you were just using Map Travel to fade out and back in at your destination. This same system could also work to bring about random encounters again... If one is detirmined by the game to occur, the PC fades into an ambush (or benign encounter; somewhere between point A and Point B, instead of where they were headed to; and from there (after the battle or talking), the PC could Map travel again, or walk the rest of the way.