Joni Ernst is a nice person and would maybe attract women. She also was active miliary. I don't know why she supported Rubio, which certainly is a big negative. However, she has urged party unity behind Trump. That said, imho, she lack sufficient experience for VP.
I don't personally like Newt but he has experience and knows the ropes. And he is a very effective speaker.
I like Sen. Session the best, but there was one report of him indicating he wasn't interested in VP slot.