With associations, you'll face associations with roughly the same quality as yours regardless of your association level.
What will happen if you have a tanking member is, the average quality of your opponents will be higher than the average quality during the previous season. That said, if its your strongest member that is tanking, it shouldn't hurt you, because that player will be able to offset his quality boost with loans. If it's one of your 3 or 4 weakest teams that is tanking, there is no advantage to tanking, and actually it will hurt your association, since the higher an associations's average quality, the higher the odds of playing against an association with 6 actives.