Gridania and Ul'dah both have varied areas but the zones have too much filler in them. If most of the pathways were removed from The Black Shroud and the open areas in Thanalan made more compact, they would look completely different. Especially when new regions are released and players can level in more places, there is even less of a reason to keep the regions as-is. However, even a 'simple' task like this needs a huge amount of work and it would not be surprising if SE didn't put resources to it. I can see them making it so we'll move from one area to another much faster instead. For example you would stay in Thanalan for 15 ranks, then move on to Coerthas until rank 25, then to Mor Dhona until you hit 30. New regions (or dungeons in the starter regions) would take you to 50.