I want something expandable and isn't completely OverPowered. Ideas?
There's really only one or the other. If you expand something enough it becomes "OP"
As for interesting: Gather Essence bushes which get harvested by a harvester and have an autonomous activator "use" the berries over a sewer. This will convert the exp orbs into mob essence.
Bonus: Use some of the mob essence for a mob spawner spawning blizzs to farm for cryrotheum and another for blazes so you can run on Pyrotheum, Cryrotheum, mob essence, and the solid reactant of your choice.