With entity lag being the main concern to the way that chickens are forcefully breaking skyblock, I feel like making it so chickens don't spawn by thrown eggs on other players islands (making it so the amount of egging and other various things caused by chickens are null and void on any island apart from your own.) I don't know the possibilities of this as a simple player who just wants the best for the game as a whole, however a toggle for chickens to not spawn on islands not yours should surely be a simple task for any of the coder staff members to have fun messing around with. Whatever happens to the chickens I stay optimistic.
I think this is a great idea and worth making a suggestion for! Maybe even removing chickens eggs from spawning chickens entirely too and adding a trade option in /shop for chicken spawner eggs for both Economy and Skyblock, could be that you trade a stack of wheat seeds for 1 spawn egg, and on eco 50$ per spawn egg
I'm fairly sure ocelots naturally hunt and kill chickens so try using them to kill chickens. To help with lag, you could try increasing the range that chickens stack in a higher radius.(Hence causing chickens to often group up into one stacked chicken, drastically helping lag.)