My friend is a long time member of the Pearl Jam fan club and they get to purchase tickets pre-sale and there is seniority involved. For example, once this goes official, everyone COULD have the same seniority and others that join right before tickets go on sale will still have a chance at presales and all, to make it fair. Also, there is a limit of how many can be purchased by fan club members during the pre-sale.
Just a thought. I think the Grateful Dead used to do this too. Yea, I'm old.