Hillary won't appoint more than one Senator to the cabinet. The pros of having McCaskill as Secretary of Department of Whatever surely aren't worth the cons of losing her seat.
I can't see Hillary appointing a lot of incumbents to the cabinet. She's too smart to do that, and she has a massive network of qualified supporters and yes-men within the federal bureaucracy.
I predict she appoints 0 Senators
This is getting pretty off-topic, but I'd could see Klobuchar getting appointed to something.
Again, this specific scenario wasn't meant to be taken
too seriously.