Benchmark wise the Northern Gas pipeline from NT to Mount Isa is 622km and it took 18 mths to build, so maybe 15 mths of construction. But you'd be looking at 3+ yrs of approvals before that. Expensive to build just for one project too, at best you pick up Blue as well but the majority of development atm is Taroom and further south. Finally the QGP (between Rolleston and Oomabeer from memory) is absolutely at maximum volume now so they'd need to upgrade that first, and the cartel won't pay for it themselves.
Here's some maps.
https://39713956.fs1.hubspotusercontent-na1.net/hubfs/39713956/PDF%20Files/TAP%20Major%20Pipeline%20Wallchart%202023.pdf
https://www.jemena.com.au/siteassets/asset-folder/documents/pipeline/qgp/qgp-map-dated.pdf
