Now this might not fit, since the some of the assets already exist in SWG, but new crafted structures would be great, different houses or even some of the NPC Buildings we see in major cities, Combat Guildhalls even up to the XL buildings we see out in the middle of nowhere (ACLO structure outside Dearic springs to mind)
For non-asset idea. Something huge I always thought SWG needed was a terraining tool being added to Mayor's list of powers, especially if you set yourself up in a nice area, but the ground just has consistent dips and trenches, makes it hard to design a city out the way you and your friends really want to when you have to fight the terrain.