I don't think there's one change that could be made to fix things - it's probably gotta be a review of the whole draft/free agency/salary cap combination.
Something like the bottom 8 sides getting an extra pick each before the draft proper.
Priority Round: 18, 17, 16, 15, 14, 13, 12, 11
Round 1: 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1
Round 2: 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1
So the wooden spooner gets Picks 1 and 9. A team that just missed finals gets Pick 15 or 16. The premiers get Pick 26.
Band 1 free agency compo - end of priority round
Band 2 free agency compo - end of round 1
Band 3 free agency compo - end of round 2
(Marquee players band 1, Best 22 types Band 2, depth players Band 3 - would need a new model to classify players)
Shouldn't be any issues with teams trying to tank to get an extra pick, because the teams sitting 9th and 10th are usually within reach of finals at the end of the season and that would/should be a greater prize to chase.
Further assistance should then be limited to AFL grants for facilities, or extended spending caps (with possible financial support) for coaching/support staff. If a club is struggling to retain and develop players effectively, more picks doesn't help, but improved facilities and extra/better coaches might.
That's my train of thought anyway. Probably full of holes, but I think it at least provides a framework where the bottom sides get to bring in talent, the top sides get to be top now but should slide sooner, and the basketcase clubs get administrative support to help them catch up.