I think fans in Australia and New Zealand are too fickle to attend winter games. They barely leave their TV's for games now, having them in winter will worsen that problem as it's "too cold outside"
Maybe in NZ, but the other winter football codes in Australia get pretty good attendances, esp AFL which does admittedly have a lot of day games, and a very long established history of club rivalries, culture blah blah blah.
There is also a counter agrument that grassroots football (soccer) fans, are in 'football mode' in winter, and the thought (esp for kids) of playing in the morning, then watching their local A League team in the arvo/night is more natural. For example a lot of them in summer will be in 'cricket mode'.
Also as article mentions, biggest challenge for fan attention/eyeballs in summer, may well be all the round the clock TV coverage of top drawer European leagues. That sort of stuff only an indepth report with lots of surveys would sort out.
Bigger obstacles would seem to be big drop in Fox Sports' cash (finances game after all), and other stuff like stadium access around other winter codes.
It's probably what about 10-20% of the total A League games that are affected by extreme heat. Is that enough to move the league to winter? Maybe not a full summer break (Fox won't be fans), but some split rounds, so for say a month, players only play every fortnight. Or enlarged squads/benches, so resting of say older players is somehow more incentivised. Apply for a FIFA exemption that if temp is above 33 degrees are allowed 4 subs??
I'd say the answer is somehow trying to work around the problems of summer, rather than a move to winter