Actually I asked him about her poses and he knows she is... not optimal, and he's been trying to adjust her, but he can't quite get her right either.
I personally suspect he'd have to redo her from the ground up, and just really doesn't want to bother. Not because he hates Jean (he might, he might not, I don't know - as Gwen says, in most things she is bland as cardboard), but because starting over on something you already did once is a drag, very hard to be motivated on it.
At least that's my theory.
As for the next girl, he said after Gwen he'd have a poll on his Partreon page, so it will be down to who he picks for the poll, and then who the Patrons pick from that.