The inland sea idea was from memory a plan to channel floodwaters from the north down to Lake Eyre, but the freshwater volumes needed to do that would not be available given the southern half of the land is getting hotter and drier.
We also need to save as much fresh water as possible in our southern dams like the Hume as they are deep and have less loss due to evaporation.
IMO a pipeline from the north that is getting wetter is becoming economic as we have solar power and battery storage --making the once prohibitive cost of pumping water in pipelines much cheaper.
As well, we are getting high prices for our food exports to Asia and a pipeline will provide a sense of sense of security for farmers in the Murray Darling
--something needed if large long-term investments in horticultural projects are to be made by investors.
