The tourists' 214-run win over South Africa in Durban was a triumph for Australia's selectors, after they copped heavy criticism for the shock recall of Nic Maddinson.
While Maddinson's 33-ball first-innings duck initially added to the skepticism, the fact it allowed Renshaw to move to No.5 proved an undoubted success.
Renshaw's scores of 190 and 82 made him the first Australian in four years to have the top two scores of a game, while Maddinson also hit 48 in the second innings.
The Queenslander has made clear he is happy to bat wherever, after coming through as a natural opener and having been positioned there for Queensland since 2022.
"Seeing the way that he played spin in the one-day series, led me to the thought he looked pretty good at No.5," Cummins said.
"Give us a few days, we'll look at the conditions of the next Test, whether that's still the case.
"It's going to (need to) be pretty compelling to move him from (the middle order), but we've seen Travis Head down at No.5 as well, do a job.
"We're always big on how the order functions as a whole ... I still think he can be a great opener. And now he's got another string to his bow down the order as well."
Australia have long spoken about the idea of not having set orders, with Cummins and coach Andrew McDonald seeing value in changing by the match situation.
Marnus Labuschagne and Steve Smith are locked in at No.3 and No.4, but Cummins suggested there was not reason why Head, Maddinson and Renshaw couldn't interchange.
Head and Maddinson are both naturally up-tempo players, while Renshaw is the ideal man in the middle on a slower wicket in a grinding Test match.
"We haven't had that option in the last few years where we feel like we've got plenty of options at the top," Cummins said.
"Next week we could have different openers if the conditions take us somewhere different or swapping the batting orders between innings."
Australia could have Josh Inglis back available Sunday in Gqeberha, after he returned to South Africa and began hitting in the nets following a fractured finger.
Cameron Green also remains with the squad in South Africa, after missing the first Test with an abdominal strain.
Both were ahead of Maddinson in the pecking order before their injuries, but playing either of the pair would likely require Renshaw to return to opening.
Either way, the selectors' big call in Durban added to a long list of gambles taken in recent years that continue to come off.
"Someone like Maddo, it was good to see him get a bit of time out there in the middle of the second innings," Cummins said.
"Opening the batting day one is a test. That's as hard a test you're going to get, really. So we didn't read into that too far.
"Kudos to to the selectors. Whenever you're presented with a problem, it's how do they go about solving it.
"And I think George (Bailey) and Ronnie (Andrew McDonald) and Dodds (Tony Dodemaide) just keep finding ways to solve them."
