Pete Gray, deputy community and cultural manager, said that also meant some staff would be working at the Sarjeant through until December 2015 but also meant increased risk to both staff and the collection.
Mr Gray said speeding up the relocation was obviously a means of reducing the risk to staff.
A second option (Option B) speeded the process up by having the gallery's front-of-house and education staff moved to the leased building. It also would accelerate shifting the collection to the ground floor of the leased building.
But under Option B opening the temporary gallery to the public would be for a further nine months.
Mr Gray said latest proposal (Option C) was the same as Option B except the collection moved to temporary storage in part of the Department of Conservation office and from there it could be moved to the second floor of temporary gallery.
He said the biggest advantage of the third option was the gallery would re-open to the public on May 12.
The recommendation was signed off by the council's operations and reporting committee this week and will go to full council for approval.
Mr Gray said costs would total about $66,000