Never played SWG, so I don't know what to tell you there, but from a healing aspect its a little hard to heal and dps while all your part is on the far left of your screen, a simpler UI that you could check and have boxes in the center or move them around the screen would be useful as that puts everything for me where I would like it.
As for the GTN 3rd party mod, well thats just a hope, the GTN is clumsy to use currently, and I am sure they are working on a change for it, but even if they can't roll one out to fast for whatever reason, allowing for 3rd party mods would more than likely make most GTN'rs very happy.
Also allowing for more than 50 GTN auctions would be great at that point.
Just my requests