I'm not sure who I'd want. but:
1. Coach K - I hate the idea of coach K. Not just because I dislike Duke, but because I don't like a long-time established college coach coming to the NBA. The style of motivation is completely different, as are the front-office requirements (shmoozing and recruiting vs. understanding cap stuff). After the pitino debacle, are we going down that road again?
2. Byron Scott makes Doc Rivers look like the best coach in the world. He arbitrarily burns bridges with talented players, arbitrarily puts players in his doghouse, and he is TERRIBLE, absolutely TERRIBLE at developing any young players. Considering that after this year we are less contenders than this year and closer to a rebuild, Scott would be a terrible choice.
Off the top of my head, here's an unemployed name right now: Avery Johnson