KOB you are actually close.
Sio at LHP, Kepu at THP, Folau at 15, Hodge at 11 and Beale at 12. I could easily be convinced to play Hooper at 7 with Philip and Timani, and McMahon to sit on the bench a la Ardie Savea. DHP would challenge one of Hodge, Speight or Folau when he is fit again. Meakes and Hunt should also be in the mix for bench spots.
I am confident that this backrow would operate more efficiently against top opposition than Cheika's present one. Lineout would definitely be stronger, and the halves would be more consistent than the present combination.
You may be dismayed that I have included only 5 Brumbies, but I've never taken the view that parochialism should guide team selections.
EDIT : I should not have forgotten Holloway at No 8 in place of Timani too when he establishes his fitness.