Add per island upgrades for various perks, some of the following VIA Vault Eco;
Typing /sky upgrades will open up a Basic GUI that lists all possible upgrades, the current level of that upgrade and then all of the sizes... with the price to upgrade it (Clicking it upgrades to the next tier)... THESE ARE PER ISLAND, SO YOU COULD GO FIND AN ISLAND WITH MAX DESTROY RATE AND USE IT
Island Size upgrades (If you want to be lazy and bypass building Value up to naturally grow your size, you can purchase starting sizes.. same as if they had the perm like for ranks)
Member Upgrades (Same as Island Sizes but for Max Team Sizes)
McMMO Cooldown Upgrades (McMMO already has this built in, just make it per island if bought... as if the rank had it)
Faster Spawn Rates for Spawners
Faster Crop/Growth Rates for Farms
More EXP Drop Rates (i.e. 1.25% more EXP dropped, etc)
Decrease destroy rate when applying enchantments on your island (Not sure if this is possible, haven't checked out their API to see all possibilities)
Increased Loot from Mobs
Hunger Upgrade to decrease island hunger loss
Entity Limit/placement (per item) upgrades?
Upgrades for Cobble Gen spawn rates (and ore increase)
Add per island upgrades for various perks, some of the following VIA Vault Eco;
Typing /sky upgrades will open up a Basic GUI that lists all possible upgrades, the current level of that upgrade and then all of the sizes... with the price to upgrade it (Clicking it upgrades to the next tier)... THESE ARE PER ISLAND, SO YOU COULD GO FIND AN ISLAND WITH MAX DESTROY RATE AND USE IT