Oh, I definitely think Handmaiden and Disciple should both have been in the party. Mainly because Nihilus makes no sense if you don't have the Disciple on the team (and high influence with him), and Atris makes no sense without the Handmaiden. But one of the things I liked the most about K2 was having optional characters. If they could just to make it so that everything makes sense whether you have one or the other...
Oh, and I'm fairly certain there will be no Jedi Wookiee. After all, LA put the kibosh on Sith Hanharr.