Didn’t they try 16 a side in the VFA?
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Yes they did and it was effective even though a long time ago.
From...https://www.theage.com.au/sport/afl/sport-thought-stop-mass-gatherings-go-16-a-side-20200314-p54a1p.html
"When the VFA played 16-a-side between 1959-1991 they scored more points than the VFL.
Brett Anderson, who is now a Port Adelaide recruiter, pointed out in an excellent
Inside Football article in 2017 that the VFA outscored the VFL by nearly 20 points a game during that 'sweet 16' period.
In 20 of the 33 seasons the leading goalkicker in the VFA kicked 100 goals with only two players repeating that feat in the state league competition since they reverted back to 18-a-side. Last year Port Melbourne's Jordan Lisle won the VFL goalkicking medal with 40 goals while the Giants' Jeremy Cameron won the Coleman Medal with 67 goals in the home-and-away season."
Current AFL player fitness and congestion makes the option worth trying imo.