If they keep the number of leagues per level capped at a particular number it would be easy to maintain a pyramid structure.
So,
perfect 1 -- demote 48
diamond 48 -- promote 48 demote 240 (5 per league)
gold 60 -- promote 240 (4 per league) demote 300 (5 per league)
silver 75 -- promote 300 (4 per league) demote 300 (4 per league)
bronze 75 -- promote 300 (4 per league) demote 300 (4 per league)
iron 75 -- promote 300 (4 per league) demote 300 (4 per league)
stone 75 -- promote 300 (4 per league) demote 0
rookie ?? -- promote 300
This system works as long as they get 300 new players every week. If not maybe a bell curve rather than pyramid is what should be the goal will fewer leagues at the bottom and the largest number in silver/bronze.
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