The only thing I can see is for them to drop the +50,25, 0, -25 point bonuses for placing 1st-4th in the weekly associations and instead replace them with bonuses for winning league, say 50 for first place (x6 is 300pts possible) 25 for 2nd, 20 for 3rd. Teams that don't promote will automatically have a -50pt penalty tacked on to their association.
This way those teams that have 3 9* teams that tank will eventually suffer.