Yep, i think that right now, Clinton has some tough options to weigh.
What does she need most? I still argue that with the popularity of Sanders, and the amount of new progressive voters he created - She needs Warren to bring them into the fold. She does well with hispanics and AA's, and does ok with women. But needs the younger white women. And Warren could be a boost there as well.
While Booker is more middle of the road, and would boost AA turnout, I think that because Trump is the opponent, Clinton will get a good amount of moderate voters all on her own.
Does she play it safe and pick Brown or Kane thinking it will give her leverage in their swing states?
More interestingly is you bringing up the coming election years. Dems could have quite a line up. Booker, Castro, Warren, Jack Conway, Beau Biden, Kirstin Gilibrand, Gavin Newsom are all interesting plays.