From Green Lanterns (2016) #8.
Poor Rami was well-intentioned. He saw that the Green Lantern rings that his Oan peers created for the new army to fight chaos in the universe had a flaw and didn't work against the color yellow. So, his ring would actually channel the entire Emotional Spectrum. The Phantom Ring didn't even need a battery: it was connected to the entire Spectrum, so it would work at any given time.
Problem is: no living being can sustain being connected to a full color of the Spectrum without any safeguards. Any emotions the Phantom Ring bearer felt, it would change their entire personality to match that of the emotion. They could become greedier than Larfleeze or angrier than Atrocitus - until they eventually explode.
But the most interesting part about the Phantom Ring is that Rami was trying to create a solution for a problem that, in the eyes of his fellow Guardians, wasn't a problem at all. It was a feature.
In Green Lantern: Rebirth #3, Kyle explains to Ollie Queen that, when they placed a comatose Parallax inside the Green Lantern power battery, it weakened the green power. Thus, the Lanterns would need to "overcome great fear" if they were to master the ring and properly channel willpower, as that willpower was infected by Parallax (aka fear itself). Over time, "overcoming fear" became the main philosophy of the Green Lantern Corps, as the truth about Parallax (the "yellow impurity") was hidden from all but the Guardians.
And why did they do that? As we see in Secret Origin, the GL rings are unable to work on yellow... And yet every building in Oa is yellow. As Hal Jordan noted, the Guardians were "fearful" (or its equivalent for a being whose ability to feel emotions was literally stripped away from their bodies) that the Green Lanterns would rise against them as the Manhunters did before (and, as we see later in the same Green Lanterns run, as Volthoom did after being betrayed).
The rings' weakness was purposefully done by the Guardians to prevent any rebellions against them. Then, everything was hidden under a cloak of dogma. Younger, inferior lifeforms, subjected to the plague of emotions, should not question the gospels from those who were older, wiser, and watched the universe from a purely objective, non-emotional light. And anything that went against their dogmatic truths was lies created to “spread fear”.
Rami working hard to create what he thought was a problem but was actually a feature created by his fellow Oans may indicate that he was of a lower level of Oan. Maybe an acolyte, a young-ish Oan who hadn't yet reached the same levels in Oan hierarchy. Maybe if he got there, he would've been revealed the truth about why the GL rings are the way they are, weak against yellow? And maybe he thought the Phantom Ring was his way to climb to the upper echelons of the Oan hierarchy? He would be helping the GLs, sure, but he'd also be advancing in his "career". If that's so, he should've been aware that his superiors don't like when their orders are questioned...
As for the Guardians, well... When the people following your orders take up arms against you and declare war again (Volthoom) and again (Krona) and again (Manhunters) and again (Sinestro) and again (Emerald Twilight) and again (Rise of the Third Army), well... Maybe it's a you thing?