Definitely keep it and improve it.
Having to start from scratch would be a huge mistake.
Sure, HAL doesn't have the power base or tifo of the old NASL but it's got a good business model and is slowly, but surely, improving as a league year on year.
We just need to buckle down and make good decisions that make sense on a financial level AND continue to increase the fan base of the league.
I always look at the MLS (sure, the US is a huge country with a massive economy, but there's also so much competition when it comes to sports). Back in the 90s they were the laughing stock of the world - yet fast forward 25 years and they now have a great league.
There's no reason why we can't have a [scaled down] version of that in AUS/NZ.