I'm in a hockey league that doesn't cap farms. The league has been going for 13 years. Some teams have hundreds of prospects, some of which have retired. Nobody wants to delete a guy from their control if they don't have to, on the off chance that he eventually becomes useful, and it just creates a giant mess. We'd have guys rostering the Deck McGuires of the world, and it becomes very tedious to look through the farm to find interesting guys in trade talks.
I think maybe adding 1-2 spots, or adding 1-2 keepers as Dinger suggests should be the furthest we go from DDL/BBDl format. The DDL has been chugging along flawlessly for 3.5 years now.