Andy is another good shout but I don't know if he's ever expressed an interest in the role.
I think Jess is good but she'd probably be seen as an easy target by media on account of her class/the way she communicates (I don't have a problem with it, obviously, but she is seen to be a bit of a media luvvie nowadays and that could be a problem).
Angela Rayner seems to be the one whose star factor is growing... but I don't know how to feel about her