It would definitely have to be someone able to grab attention and keep focus on the character. I mean
Female Kirk should be strong, beautiful and sexy. You should want to look at female Kirk and look and look.. and follow her anywhere. She exudes confidence and touch of wildness. I'm voting for Doreen Jacobi, not well known outside of Europe, striking and interesting and not just a pretty boy (girl) to look at.
Follow her ANYWHERE!
She has some sci fi pedigree, she was in an episode of Lexx.
What were we talking about?