I think a cap on how much you can recruit, a max contract on two players of up to $2m (only one if it’s a player not developed), points system (that would be hard to implement), transfer windows. There are several ideas. The biggest reason for the discrepancy is the spine talent and the difference between top and bottom. Compare Melbourne/Roosters/Penrith even Parra who have 3-4 and even more players who are or could be very good spine players to say that of the Tigers, Warriors and the Dolphins.
I think I read an article somewhere that will be a requirement from now on to have a licence.