Every club that has an ABL Div 1 Men's and Women's team should have a team in each Division 1 junior competition, e.g.:
Central District
Eastern
Forestville
North Adelaide
Norwood
South Adelaide
Sturt
West Adelaide
Woodville
There should really only one team per division, per age level. For example, in Under 18's, you can have the above-mentioned 10 teams in Division 1, with 8 players each, making 80 Div 1 players in total.
Add that to Divs 2, 3 and 4 (Division 5 is too much I think), and you then have 32 players per club, per division. Surely numbers are such that that is achievable with quality not being sacrificed.
If there is excess numbers that the 32 wanting to that wanting to play in an age group at any club and then they miss out, then that will be how the quality of District basketball is regulated. Simply put, if you aren't good enough for one of the 32 places in either Div 1, 2, 3 or 4 in your age group at a club, then you unfortunately must miss out.
Also, to maintain quality in the juniors, there should be a rule that states that nobody can play Men's or Women's ABL Div 1 unless they play 3 games in Under 20s/21s Div 1 level for their club in the same season. That means actually seeing game time, not just sitting on the bench. I realise numbers may not permit such a rule, but it should be enforced where possible to maintain the quality at the Under 20 level and below.