I'm a big fan of upgrading those grounds to be boutique, state-of-the-art 18,000 or so seat grounds. Modeled on grounds like
PayPal Park,
Allianz Park or
Childrens Mercy Park from Major League Soccer.
Perth Red will, of course, throw a fit because he thinks every club should be playing out of some cavernous stadium. But the fact is it's better to have 20,000 people want to be able to go to a 17,500 seat stadium and have 2,500 fans unable to get a ticket because:
(a) It looks better on TV.
(b) It creates incentive to buy tickets fast if fans are on the fence about attending.
(c) It allows clubs to charge a premium for tickets.
It is better to have those games in a 17,500 seat stadium and sell it out than a 50,000 seat stadium where you get a whole row of seats to yourself.
You're also right that with less derby games in Sydney, there's less demand for away seats. Add to the fact that a lot of people just prefer to watch it on television - we had a grand final rematch last night and the game was an absolute cracker and only 16,342 seats out of 30,000 were filled.