I'm brought back to remember a throwaway line from the Season 1 episode Cat Fingers, where Garnet, Amethyst, and Pearl~ were taking the gem boat out to go and fight a "Living Island". It also brought up a blink-and-you'll-miss moment from Earthlings where Smokey Quartz dodges Jaspers attack as sye barrels into the cliffside and unintentionally releasing her army made up of forcibly conscripted Gem Monsters, and a few Cluster Prototypes. Then we get over to Change Your Mind when Blue Diamond snuck into Yellow Diamonds Palace with Steven and Connie to retrieve the Crystal Gems before helping them escape from Homeworld: the lights turn on and we see dozens of Fused Gem Shards in bubbles around them. All this got me to thinking that what if the next obstacle we have to face is the Cluster Prototypes.
Now why did I bring all this up exactly? It's very simple. Our next obstacle that the Crystal Gems could try to tackle would be trying to find a way to undo the Shard Fusion Experiments and to hopefully bring back those that were lost in the carnage of war; those that didn't make it back from the battlefield or were too far gone and broken to become Corrupted. This would be the initial end goal, but there has to be a lead-up to that point: Era 3 and the new Pink Court that Steven finds himself a leader over, Gems that had long since hid what they had wanted to become, Gems that had an understanding of the real Pink Diamond almost as much as her own Pearls did, even Pinkie Pearl herself might find herself around this trying to adjust to the thousands of years that she was spent mind-controlled by White Diamond only to wake up and find out that her original diamond that she loved dearly was given a new Pearl, was given her own Colony, started a civil war with herself, faking her own death to live in self-imposed exile, and giving her life in order to have a child: a child who had managed to free her and do what Pink Diamond had failed to accomplish in changing the Diamonds minds. Era 3 for the Pink Court could be seen as a transition period and an adjustment to a new way of life spent on Earth, probably even incorporating aspects of Homeworld into everyday life on Earth, even the construction of new structures and spires or even townships and cities on Earth populated by Gems. Some of the early conflicts could be some form of land dispute between Gems and native Humans that could be solved through trade and diplomacy, others could be in rounding up however many Corrupted Gems might be left on Earth that the sole four Crystal Gems hadn't the manpower to locate or contain: manpower which they now have in abundance, thanks to the events of Change Your Mind. Eventually however, things take a turn for the worse as a Gem City goes silent on Earth and survivors and refugees from its destruction start to arrive: telling tales of a mountain or island that moved across the land towards them. It is only here that we get into the meat of the issue: Cluster Super-Prototypes: Clusters that are larger than the more "normal" Cluster mutants, but only slightly smaller than the actual Cluster that it cannot be defeated through conventional means alone, requiring the need for super-sized Fusions like Obsidian to take them down before they could cause any more damage in their path. The reason for these Super-Prototypes to exist was to serve as some way to test if the Cluster itself could be possible to make, and that they've been asleep all this time because of a significant lack of Gem presence beforehand, with these creatures ignoring Corrupted Gems to instead.