Ryofui is on to something - certainly a factor that prevents war in the modern world is that most countries are too valuable to conquer. That is to say, trade partners are better than annexation. And in the past, such self-aggrandizing methods can let a state remain neutral as war rages around them (Switzerland).
On the other hand, simply trying to increase the prosperity if your own nation leaves you vulnerable to an enemy who doesn't care about trade, or doesn't understand the value of peace, and attacks you anyway. And getting too isolated leaves you falling behind, and being rudely awoken by a foreign power (Japan).
Moreover, Ryofui's plan hinges on his ability to magically make Qin a Utopia. Where will all that new value come from? Especially if he intends to maintain the feudal society. And if he truly cares about the welfare of the country, he would have enacted whatever reforms necessary to raise the standard of living a long time ago. Why does he need the throne for that?
If he were a man of the people, I could almost trust him. Maybe his plan involves bringing Democracy and Civil Rights to China a few thousand years ahead of schedule. But time and time again, he has shown his character - rotten to the core, and utterly self-serving.
No, Ryofui is unsuited to become king.