Why would Naboo, an upstart planet with a bit of a civil war brewing be of any interest to the Republic or the Empire?
It has no amazing natural resources, it has no weapons factories or biochemical research faclities worth fighting over. Any excursion by either planet onto Naboo would be a waste of resources. Plus Alderaan already helps us meet our pretty green planet with lots of philosophers, nobles and artists quota. We don't need another.
Similar with Dantooine, it is at this point in time of no interest to either faction, perhaps there could be a plot about rebuilding the Jedi Enclave but considering one of the worst councils in the history of the order housed there I wouldn't be surprised if they'd rather forget about the place.
The world doesn't have to be an interest to either faction but to the player.
As part of the story, the player could help with any problems that are happening and depending on their intentions, can use this to recruit the people to help either the Republic or Empire etc.
Plus the universe is a big place, why just visit worlds that have some sort of strategic importance when you could go there simply to explore. Anyway you could suggest worlds which you'd want to see.
It would be a bit of a waste to make a whole planet dedicated to just one or two classes, as that means they'd have to make other planets to fill in that gap in the plot for the other classes too.
While it might be neat to have a planet just for "your" class again after the starter planet, it would require a lot more resources than designing a planet with one, or both factions in mind. So again, not a bad idea, but I think Bioware won't commit the time resources to it. And even then any suggestions taken into account will be quite a bit down the pipeline as currently the writing team is currently penning stories meant to be added into the game in 2014, according to a recent interview.
Well Roon is a very big world to explore with huge oceans, bogs and ice mountains, it could be the first which is level 1-30. However the idea is if the Taung were playable and no matter what their class is, they start there for a few levels and then head off to either Hutta or Ord Mantell.
And make it sandbox content!
Yes! Rather than using taxis and shuttles to travel between city platforms and gas stations, it would be the perfect oppertunity to use your personal ship to travel freely between them