Well, it also has the problem in that it completely destroys the entire setting and the entire past of the setting in one stupid idea.
The problem with all the neat ideas about Infernals is that Infernals can not be more powerful than Solars. This is a truism of the setting. Solars are the most powerful of the Exalted, definitionally. So if an Infernal can do it, a Solar can do it.
Then understand that Infernals can become as powerful as an unrestrained Primordial.
Which means every individual Solar has the potential to equal an unrestrained Primordial.
Which means that stuff like getting the entire Solar deliberative together to do stuff like, say, the Salinian Working is ridiculous, because now we know that every single Solar in existence is at least as powerful as She Who Lives In Her Name and Adrián , who were capable of doing shit like destroying significant chunks of all existence retroactively (ie, atemporal attacks) and fighting off the entire Exalted host single-handedly.
Not only does this entirely break the Primordial War, it also breaks the Usurpation over its back. Because if the Solars, at the height of their power, could be taken down by the Dragonblooded and Sidereals, the Solars are now superflous to the setting since you could have won the Primordial War with the same force. Either that, or they aren’t as powerful as we thought.
Not to mention stuff like the soul hierarchy stuff meaning that every Infernal came with an army of potent magical supergods of their own, so Solars suddenly have to have equivalent tech so a Solar can one on one duel with a Primordial and his entire soul hierarchy at the same time which leads to all sorts of ridiculously broken bullshit.
Plus all sorts of other stuff, like the fact that it was made clear that Primordials could fix the Great Curse, so if Infernal are as powerful as Primordials they can fix the Great Curse which means that Solars can, singlehandedly, fix the Great Curse. You know, with just the right Charm.
This also lead to a Race To Essence 10 mentality, since once you set the high end of PC power at “Primordial” everything else just becomes meaningless. The Elder Problem became magnified a billion times because in order to compete with the suddenly effectively omnipotent Essence 10 Solars, Lunars and Sidereals had to be “one step short of Primordial” level power (otherwise, again, how could they possibly have killed them back during the Usurpation) and on and on.
Plus, the Charm trees made absolutely no fucking sense as Primordial Charms. Why would a Primordial need a Charm that say “I don’t need to sleep” or “I don’t need to eat”? These are Charm extremely useful to humans, who eat and sleep as required, but a Primordial is not a human and never had human foibles or weaknesses, so why would they need to sleep? “Needing to sleep” is not a universal weakness inherent to the cosmos.