This is what Referback does – last referrer, but that player will belong to him/her throughout the group.
There are many ways to look at it. With Referback I will often send players that already belong to someone, but I also know the fresh ones I send will belong to me across all properties. So my player value is a lot bigger, while my player base is smaller.
It evens out the same way either way IMO and I promote either one of these comission structures. In the case of Referback, affiliates voted on this and voted in the current system.
The main issue in tracking remains that the last referrer should be the one to get credit, and most programs do it that way today.