That other thread was for starship captain, this is for any cast member, regular or recurring. For example, I could see 31 year old Summer Glau being Operations or Science Officer.
Speak of the devil, somebody beat you to it:
Ensign Charlotte Ainsworth, U.S. S. Polaris
(from Dave Metlesits's Star Trek: Polaris page
IDW just beat you to it: Captain Jane Tiberia Kirk Takes Command