Eduard Schweizer, "The Son of Man," JBL 79 (1960): 119-129.
Schweizer argues that Jesus adopted the title, "Son of Man," because it was ambiguous. Schweizer contends that Jesus viewed his mission as the fulfillment of what Israel failed to do in the trial context of the suffering and exalted righteous. Schweizer contends that the title took on various meanings in the early church.
Some valuable insights. Synopsized in his Good News According to Mark. Very similar position to M. D. Hooker on this issue.