that could happen, then 70/70 thing was an example
basically a rule made by Mojang that if a server has purchasable ranks that could give the ranked player an advantage against regular players in any way the server could get shut down, CC making it fun and fair to all decided to give ranked players cosmetics
as
@Buuuddy said they could make it 50/50 + 10 reserved for the obsidian ranked players
Well i stated above that Emerald and Obsidian ranks have too many similarities making Obsidian nearly equal to Emerald but u just pay extra for it, adding a new perk to the obsidian rank could make more people wish to purchase the rank and make obsidian ranked players feel more "Special"