As some pointed out, Shaka Smart would be a solid addition to that list. I clearly on the fence as to who I would like to take over when JC hang's 'em up. As successful Smart & Stevens has been, I've only seen a handful of their teams and never really took a close look at their whole style of play. Neither really has much of a track record with recruiting with the big boys. They've both done more with less, which was a hallmark of JC's early success, though one could argue that he's still one of the best at finding diamonds-in-the-rough and developing them into very good college players and often gets them into the NBA.
I really like Ollie. He's had some success with recruiting elite talent. He simply has no head coaching experience, so it's impossible to determine what system he would run and how successful he would be. To that point, even the mid-major coaches, it's hard to tell what stuff they might run if they had better talent. For example, JC pressed the h*ll out of their opponents early on, because he simply didn't have the offensive talent he's been getting since the mid to late 80s. Shaka likes to press, but would he do so w/ better talent, and if not, how good an Xs & Os guy would he be running something different than he has been. Note that I've not watched all that close as to what type of stuff he runs on both ends of the floor.
From the little I remember from Stevens, I thought he was pretty good with the half-court offense, and his teams seem to play the hard-nose half-court D that we see at UConn. They didn't look particularly good against UConn in the 2011 NC, partly due to UConn playing their D at a very high level.
What would be a very interesting question...well I would think it would be interesting...if you could have any active coach regardless if the coach could be had, who would you want? I think I might throw that one out there.