4* crystals
I rarely get a new 4* champ from the 4* crystal now and as they add more I seem to miss out on the newer champs, so why couldn't you do what you do with the 5* crystals and have say a 4000 shard 4* crystal that only contains the last 15/20 champs to be added to the standard 4*, still have the same amount in the 2000 shard crystal.