Gio Van Bronckhorst would be my choice, did a very good job at Feyenoord before stepping down last summer and was being linked with Man City as a possible long-term successor for Guardiola afterwards. He signed on with a club in China in January but I don't think that would make him impossible to get.
Other than that I'd take Cocu or Howe as well and I think they'd both be interested.