I'm not as afraid of MCW as you. He led all of college in steals, and averaged 5 rebounds a game, which to me means he has the quickness to disrupt opposing point guards, and enough athleticism/strength/toughness to go in for rebounds. His turnovers are a little high for me, but his role in that offense was a ball-dominant point guard. I see him with a Rondo ceiling, and would happily take him at 16. He could flame out, but so could a lot of players in this draft. He's one of the few I think has all-star ceiling if he puts it together.
Zeller I share your concerns about, but as you say, he'd be a value pick at #16. I think someone may be disappointed if he goes top 5, but he has a very diverse offensive game. I'm putting together a post on the big 10 draft-eligible players, and will talk about him more.
Of the players I see likely in our range, I'd most like to stay away from Olynyk. His abilities scream flame-out to me. And his hair is turrible.