Windfall means something very specific too.
It's not just profits, it's profits exceeding expectations.
So if the company expects to earn 1 billion dollars profit and actually earns 1.1, it's only the .1 that's a windfall.
And as you say, he's a weasel who is likely to define "public good" as "In Clive Palmers person interests".
In order to pay for the legal challenge the government should remove all mining and fuel subsidies for the sector, or institute a subsidy payback scheme, like hecs.
They should also charge for the groundwater used by his mines and revisit lease and royalty agreements.
I'm pretty sure the government has immunity from being sued for law changes.
Now if they had fucked up in some way, like failed to give you something you were entitled to, THEN you could sue them.
But for changing the export laws or a trade deal?
You'd need to establish a "right to proceed" with the High Court.
And the High Court is going to tell Clive to pound sand.