I'd say Christian is certainly playing as an all-rounder. His batting depth for me is still crucial, since for me having a solid batting/all-rounder @ # 8 in a T20 XI is very important.
Watto obviously is the main all-rounder. But i won't call Maxwell a full fledged main all-rounder yet. His bowling is still slightly iffy and is not one i would trust to bowl in a pressure situation like David Hussey's off-spin for eg.
Picking another bowler based on the options in the squad in McKay, Hilfenhaus or Doherty doesn't give me much confidence. If it was Bollinger, Harris, Pattinson or Nannes to choose from instead then maybe.
Too much responsibility has been placed on Starc/Cummins, an experienced proven T20 quickie in the absence Lee (Harris, Bollinger or Nannes) should have been in the squad. And, i'm very nervy about Watson opening the bowling suddenly. Thats fine when he does it for his joke IPL team - but not for international cricket against strong batting line-ups.