So, we have an essence sundering option, which takes a greater essence and turns it into 5 lesser essences. However there are numerous complaints about it being hard to acquire greater essences... or the outright removal of different types of essences. I'd imagine it is because of the pain it may be having a flood of lesser essences but not enough greater essences.
Why don't we have an "essence unification" option as well? This would take lesser essences and turn them into a greater essence. It could just be 5 lesser essence = 1 greater essence or 6 lesser essence = 1 greater essence.
Or perhaps we could mix it up a bit. Add a new crafting item (say, cream of conjunction or something less cheesy) in which you buy from plat. So it would take 5 or 6 lesser essences + <new item> to make a greater essence.
Or, we could even require a lesser essence previous in the cycles of transformation. For example, divine essences can be transformed into a good essence. So if we want to combine our 5 good essences into a greater good essence, we also need a lesser divine essence. ... or maybe we can go the other direction in the cycle, requiring a lesser chaos essence.