This is quite an old post. But I really think Hoth is a bad choice. The battle of Hoth is the only thing that makes Hoth significant. There are no cities or ongoing battles and making it some sort of repeating battle of hoth is a bad idea. I also think that any planet that has to be done like Kashyyk (instanced) is a bad idea. I think that concept works well on Kashyyk but it just does not feel like SWG to me... I also think Korriban would be a bad choice. It does not have any great significance in reference to SWG's timeline and I don't think there are much but ruins. I think Korriban would only cater to Jedi players.

Any new planets that are added should have at least a few of these:
1. Have significance to the GCW era
2. Have several cities/outposts
3. Have rebel/imperial/neutral interest/content
4. Be enjoyable to a wide range of players
5. Have the real SWG feel :P

I think Kessel would be the best option for a first planet precisely because it is graphically redundant. It would make good practice for those people developing it before trying to tackle something more complex. Also, you could get away with making it smaller, like only 8km^2, further reducing the workload. After Kessel, Geonosis probably is the best option, and Kashyyk would be good, too. Hoth would also make a good Rebel-only planet, as it is iconic, has the same benefits as Kessel for being easily produced, and would get the Rebels off Corellia (which is far too populated to make a believable hideout, anyway). Later on, there could be an epic GCW event there between the Rebels and the Imperials as they fight on several battlefields and through missions, not unlike the monthly GCW storylines they did.

I'm more of a neutral guy here so Nar Shadda is a great place although you're going to have a hard time to come up with the graphics for that. However, Bespin Cloud City would be a great trade/recreational zone. You could implant Rebel and Imperial interests and there you have a set of missions to play with. A reason for Cloud City in particular is that you do not have to essentially create the whole planet (which is inhabitable) but just create it as a City with focus explicitly on the interior. Who knows, you could look out the window and see some clouds or pilot the Bespin Cloud Cars but thats probably the extent of Bespin.

The problem with Bespin is it would have to be a little like Kashyyk, in that it would only be a few zones instead of a whole planet, and it would only really be there for the quests that take place there. People would likely only hang out as long as they had quests to finish. Another problem is the inability to place structures. In order to make it a really vital planet, you'd have to find some way to integrate flight and there would have to be things for all professions to do there, gas mining for the merchants, for example.

I could see the JTL engine being utilized outside the floating cities and the regular game engine inside the cities, but this would essentially mean creating two, or even three planet zones (if the sky and the space are separate zones), and the ability to create a whole floating city using the political mechanics, but that would be a lot of work to get right.