I rated this thread.
On reflection.
Sites need players & affiliates to get them those players.
Affiliates can convert but the best conversions are long term MGR players.
Players will stay with a site after their first deposit only if they win, otherwise they generally move on to the next bonus.
I think the cashback idea is best for the site/affiliate/player.
You can translate that into other forms such as free spins for the weekend but it brings a dead player back
IMO, a win win situation all round. It all comes down to loyalty.
The site want the retention rates.
The affiliate want regular mgr payments
The player wants a non conditional reason for coming back to a site who skinned them.