The FFA are totally taking the piss with this "prove you're not a liability" line.
The Nix are not a liability to the FFA in just about any commonly understood sense of the term. The club operates at close to break even and any losses are covered by the owners. The money that the FFA pays the Nix is not a donation or subsidy to football in NZ - this a myth that needs to be dispelled. It is exactly the same amount they pay all the other clubs and it buys them exactly the same thing - a squad of 23 players who play at least 27 games a season on the telly. The Nix get a 10% share of the TV money (that the FFA allocate to A-League clubs) and they provide 10% of the content. They also provide that content at much lower risk to the FFA than many other clubs.
The only way you could possibly call the Nix a liability is if you very specifically frame the question in terms of maximising the potential amount of TV money that the broadcaster is willing to pay, and that is driven by ratings. It's true that the Nix ratings are not the highest but they are also no lower than a few other clubs. Also, if you replace the Nix with another club it has to rate higher than the Nix and that's not a given. The FFA seems to think that derbies rate higher so is looking at an extra Sydney team, but that would mean going from 3 Sydney derbies a season to 9. It could actually dilute the interest in derbies (there would be a derby every 3 weeks) leaving them back at square one, or worse. A more sensible strategy would be to go back to the content part of the equation and expand the league. More clubs = more games = more content.
Their attack on the Nix is an ill-conceived, slightly desperate, knee-jerk reaction by them to an overall ratings plunge in the league, which the FFA themselves are accountable for and which they don't seem to know what to do about.
The good news is that quite a few people, including club owners and media, seem to have seen straight through this. The FFA won't back down completely but I'm hopeful that Welnix may now be able to take up a 4 year extension on much more agreeable terms if they are also willing to compromise.