Robertson's side have won their first two games of the 10-week competition involving New Zealand's Super Rugby teams and can overtake the unbeaten Blues at the top of the table with a win away to the Highlanders on Saturday, live on Sky Sports.
"Certainly from a New Zealand perspective, we know what the public want. and we've known for a long time what the public want", Impey said.
"We've been able to use the current five to field a pretty decent All Black team over the years with very few hiccups".
Adding New Zealand teams would create an extra layer of excitement for supporters but would undoubtedly be a complex process.
Despite four New Zealand teams making the finals, crowds fell by 6 per cent in 2019 while Sanzaar partners Australia and South Africa had issues of their own, with Australian Super Rugby teams struggling to be competitive since 2013.
"The risk you are running if you go down that line is that a watering down of high performance".
If Carter gets through the match unscathed, he'll likely become available for selection with the Blues for the remainder of Investec Super Rugby Aotearoa.
"The challenge is that it's pretty hard to run a sustainable competition with five teams".
A small dose of high-quality football works wonders - which is the situation that New Zealand has now found itself in - but if the same five teams play one another week after week, year after year, then the product will become stale over time.
New Zealand Rugby remains open to working with Rugby Australia on a possible trans-Tasman competition.
New RA chairman Hamish McLennan has suggested that a trans-Tasman competition is the future and Impey certainly hasn't ruled that out.
"We're open to it all", Impey said.
Rugby Australia, who are in dire financial straits, will be desperate to come to an arrangement for NZR for the future. "We've got a completely open mind as we plan through".