It's easy to have more shades of grey than the Garlean Empire, given the Garlean Empire is almost entirely terrible. The Empire is evil by design (as has been boasted about by Emet-Selch), almost fractally; it's evil to individuals, even under its alleged protection (what happened to Fordola's parents, which happened under the "decent Legatus" Gaius), it's evil to groups of people ("good" Regula was willing to wipe out the Vanu Vanu on Varis's orders), and it's evil to the Empire itself (as Emet-Selch carefully arranged, for maximum chaos).
I've been fairly careful and precise when I say the Garlean Empire needs to be torn down. This is completely different and distinct from saying that Garlemald needs to be torn down. The Garlean Empire has literally existed for only 55 years at this point, and it has already caused mass suffering and pain on three continents. Hence why "the empire", and more specifically the system of imperialism, must be destroyed and stopped. Garlemald itself is perfectly able to survive and even thrive as a non-Empire, given it has existed as a major polity for like 500 years before turning into an Empire. (Before anyone claims "oh but they were persecuted", that happened about a hundred years before Garlemald existed. Garlemald as a nation was formally founded after it had taken over all the territories and settlements in its vicinity.)
So Gaius automatically obeying the orders of Emperor Varis at the end of 5.0 is kind of puzzling, since that implies Gaius follows the ideals of the Empire, rather than of Garlemald. Maybe to him it's the same thing (he probably has only known about the Garlean Empire), but the Garlean Empire is only one of many possible political systems available for Garlemald, and given the sheer chaos it caused, I would say being an Empire is not a good thing.
(The obvious route would be returning to the Garlean Republic, but I figure it's also fine if they want to try other political systems. The Holy See of Garlemald, perhaps?)