Co-ordination is the market operators job. The states already have to work together now.

The point is that modelling shows that we can achieve a renewable grid with existing technology let alone with the efficiency and cost improvements we are seeing on a regular basis.

Then there's the real world examples such as batteries doing amazing things . At large grid level sizes. There is a tidal wave of technology coming that will make today's tech look pretty ordinary . Especially the Dutton brain fart.

Deeper, longer, cleaner: Big batteries extend domination of California’s evening demand peaks

https://reneweconomy.com.au/deeper-longer-cleaner-big-batteries-extend-domination-of-californias-evening-demand-peaks/