Mr Barrett may live closer to Adelaide than Sydney, but after years of taking students 17 hours by train to visit the AGNSW - funded by sausage sizzles, raffles and sales of his own art - he had a long list: More space to put bags and take notes, a chance to see behind the scenes and talk to artists and curators in the sophisticated language required to do well in the HSC and explanations about the role of installations.

"Quite seriously, I'd get kids who'd get off the train and say it was the best week of their lives," Mr Barrett told consultants and gallery staff surveying the public on Broken Hill's main street last week. The visits had helped many of his year 10, 11 and 12 students get great HSC marks and pursue higher education outside of Broken Hill.

As a result of public consultations across NSW nearly 1000 members of the public, plus surveys and discussions with neighbours, community groups and others, an art garden that will link the old and new parts of the gallery will be included in the development approval to be lodged in November.

With the entrance plaza, the art garden would create a "cultural precinct that would link the AGNSW with the Royal Botanic Garden", an idea that excited communities in consultations, a gallery spokesperson said.

She said there had also been public support for an open air entrance plaza, covered by a transparent roof, which will be further developed as the design is refined. It will include a multipurpose theatre with a focus on education and learning, which would accommodate some of the 100,000 students who visit the AGNSW from across the state every year.

The original 2015 design by Japanese architects SANAA, who won an international contest, had placed the first of the series of floating pavilions on the land bridge, and a tunnel had originally connected the old and new buildings.

But the public agreed with the former Prime Minister Paul Keating who had successfully lobbied for the expansion to be more compact. This resulted in the buildings having a lower profile, and being moved to the north east so they float down the hill leading down to include the old WWII oil tanks.

At Martin Place, a member of the public said she hoped the latest changes would result in the new wings fitting in with the landscape.

She was sceptical about consultations outside of Sydney. "I am not sure that if they are in Broken Hill they are going to give a rat's ass. But it is great to ask everyone in NSW."

In Broken Hill, a mining town that has always had a lively art scene, the response to this criticism was blunt. "It is the Art Gallery of NSW," said one person, stressing the NSW.

The director of the Broken Hill regional gallery, Tara Callaghan, who was involved in talks with gallery staff, said the arts had always been big on the hill, and it was unusual for a town with a population of 17,000 to even have an art gallery, let alone one worth $10 million collection. There were so many small and independent art galleries that visiting them was like playing an art version of Monopoly.

For gallery staff involved in the nine consultations, ranging from Orange to Fairfield and Newcastle, it was also a way to deepen existing relationships that have resulted in a two-way stream of visiting artists, exhibitions and school programs.

Heather Whitely Robertson, the AGNSW head of learning and participation who travelled to Orange and Broken Hill, said the consultations were very much about understanding the needs around community engagement, and within the school sector.

"We know regional schools have fewer resources, and we really trying to find ways that we can utilise our brain power" to address the problem. For instance, a teacher in Orange had a "fantastic idea for creating an Instagram resource that was feeding in from a variety of galleries around the state", including the AGNSW, to make an artwork of the week.

For most blase Sydneysiders it was hard to imagine the impact of a trip to Sydney to visit the AGNSW, the Museum of Contemporary Art, Carriage Works and the White Rabbit in Chippendale specialising in modern Chinese and Asian art, said Mr Barrett, who is now retired.

"You got to do White Rabbit, because the HSC's whole idea is seeing whether you can apply what you have learned to unknown artists. So the easiest way of doing that is Asian art."

These visits had made Chinese artist Jiawei Shen "iconic with my students", who were mostly exposed to bush art at home in Broken Hill.

"We talk about why this is important to the human condition, and that's how they get a great HSC mark. You'd talk about how Jiawei Shen [now based in Sydney's Bundeena] put his life on the line to talk about freedom and multiculturalism, and how he was willing to be arrested and be put away forever. And how he has mobilised international community to keep him out of jail so he doesn't just disappear. They love it," he said of his students.

Consultant fees for the Gallery's nine recent Community Information and Feedback Sessions across metropolitan and regional NSW totalled $39,000, which AGNSW director Michael Brand described as "Money well spent".

In a letter in early October to stakeholders Mr Brand said SANAA's evolving design concept responded to the unique project site with a series of pavilions that cascade from Art Gallery Road towards Sydney Harbour and Woolloomooloo.

"The pavilions will sit low and lightly on the site, shifting gently along the natural topography of the land to preserve existing trees and sight lines. The subtle profile of the pavilions will also complement and preserve the dignity of the existing Gallery building, and together both buildings will create spaces to bring people together and foster a sense of community, imagination and openness."

He said the new building had evolved from the concept envisaged in the design competition, driven by feedback provided to the Gallery over the past two years which had resulted in the new building operating as a standalone building linked to the existing Gallery building via a two-acre public art garden, which will feature a covered outdoor entrance plaza as well as sculpture, installations and landscaping.

"The new building will have a more compact footprint than envisaged in the design competition with significantly reduced built structure on the land bridge over the Cahill Expressway," he wrote.

The project was originally estimated to cost as much as $450 million, but the current project is now expected to cost around $344 million.

Julie Power travelled to Broken Hill as a guest of the Art Gallery of the NSW.