How formidable would she be? I don't know, but if she manages to win the primary, that'll be evidence that she can do the running-for-office thing, which is the big question I'd have about her at this point. Overall, she looks like she'd make a good Senator -- populist heart, technocratic head.
The funny thing is that if Brown follows Ezra's plan, he has to do it either quietly or effectively. If he's publicly supporting her for confirmation and she doesn't get confirmed, his criticisms of her in a general election are going to look silly.