I know there is a who would you like to see thread, but this is a realistic who/what possible addition to the crew of destiny.
I think one such character could be:
They drop out of ftl and find a sort of shielded, hovering floating satellite. There is a person in there. They think she is in need of rescue so they disable the shield that contains her and free her. They have her as part of the crew.
For those of you who may have watched Batman Beyond, I think she could be like pseudo-Ink character/or the bad guy from terminator 2. She is a shapeshifter. A race locked her up and she is now hell bent on revenge. She tries to keep her powers a secret but kills any who may find out or get in the way of her revenge. The shield was powered by the sun and she does not eat but use the suns energy as well.
They may come into a world that is civilized and heavily populated. They could use a guide. One such character addition could be a thief/smuggler of sorts. They usually have a good knowledge of regions/peoples.
Any other character ideas?