Having been trusted with only 11 bench minutes across the four Tests this year indicates the 35-year-old is on the outer but Cheika warned to read little into his line-ups so far.
"When we go into the selection process we're not even just looking at the players who have been in the (Rugby Championship) squad," he said. "We'll take into consideration everything around the complementary nature of players and get the best possible fit of preparing for all the situations we'll come up against in the World Cup itself."
Simmons, Kepu and Polota-Nau are in their 30s and share 291 caps but they'd be unlikely starters in the big tournament games.
Their value, like that of 118-cap Ashley-Cooper would be as much for their off-field leadership.
The team that was largely unchanged across both Bledisloe Cup Tests will form the core of the squad, with the trimmings setto comprise some players who have seen little rugby of late because of injury.
In that category, Petaia, David Pocock, Pete Samu, Jack Dempsey and Polota-Nau all mount strong cases for selection.
Cheika said he isn't considering any offshore players aside from his overtures to lock Will Skelton, with no word yet on whether the giant Saracens star is available.
There may be minimal space for outside backs, with Dane Haylett-Petty and Tom Banks both tight calls.
The squad's balance could hinge on something as innocuous as whether a third halfback is taken.
Former Wallabies great George Gregan believes it is imperative Joe Powell travels as a specialist backup but Cheika has hinted previously at rolling the dice and taking just two — almost certainly Nic White and Will Genia.
WALLABIES WORLD CUP SELECTION DILEMMAS
OUTSIDE BACKS
Michael Cheika won't want to overstaff the wide berths. Dane Haylett-Petty and Tom Banks could be in a straight shootout behind Kurtley Beale, Marika Koroibete and Reece Hodge.
MIDFIELD
Samu Kerevi, James O'Connor and Matt Toomua are certainties. One of Adam Ashley- Cooper or Tevita Kuridrani should get the nod although boom Reds outside centre Jordan Petaia can't be discounted.
LOOSE FORWARDS
Pete Samu, Jack Dempsey, Liam Wright, Rob Valetini and Luke Jones are all prospects to fill the last berth or two, though they've seen minimal Test time this year.
HOW MANY SPECIALISTS?
Joe Powell may be on tenterhooks as Cheika mulls the merits of a third halfback. It's the same for Rob Simmons as a fourth lock and Tom Robertson as a sixth prop.
POSSIBLE WALLABIES SQUAD
Backs: Kurtley Beale, Tom Banks, Marika Koroibete, Reece Hodge, Jordan Petaia, Tevita Kuridrani, James O'Connor, Samu Kerevi, Matt Toomua, Christian Lealiifano, Bernard Foley, Nic White, Will Genia, Joe Powell.
Forwards: Isi Naisarani, Pete Samu, David Pocock, Michael Hooper (capt), Jack Dempsey, Lukhan Salakaia-Loto, Izack Rodda, Rory Arnold, Adam Coleman, Allan Alaalatoa, Taniela Tupou, Sekope Kepu, Scott Sio, James Slipper, Tolu Latu, Folau Fainga'a, Tatafu Polota-Nau.
