I think that ultimately, there is no way to make an association draw that will make everybody happy. On the one hand, its easier for 5* associations to climb the ranks, which frustrates 7* ones. However, how many of those 7* associations will be complaining, when they play against an 8* association they can't possibly beat?
Personally, I'd like to have weighted rewards. The higher the average quality of ones association, the better of the rewards. Sure, the 7* will get better rewards than 5* associations under such a format, but 7* teams are also putting more time and money into this game than 5* teams. Plus, it will give teams incentives to improve there rosters, compared to dropping there qualities to get easier opponents in associations.