It wouldn't be the first time an author created a new planet in Star Wars and had it approved by LL. While I would prefer Kashyyyk or Naboo or one of the other established planets in the Star Wars universe, I see nothing wrong with making a new one. As long as it's well thought out, I say "Why not?"
wait, you WANT to go to Naboo? You WANT to have Gungans running around? You WANT to have to talk to them as your quest givers? Are you ill?