I don't think I agree with that. Sho is absolutely average. That's almost a point of the character. There was nothing special about him at all before 'greatness was foisted upon him'.
He got the armor because of a fluke. But the implication is that it could have been anyone.
All humans have the potential to become Zoanoids, but a G-unit removes that potential. You could well say that the Guyver represents the rejection of military authority by the common man. Chronos is the very embodiment of a military drafting young men as cannon fodder. ...Takaya-San was born in 1960, so his parents would have lived through the war. It's entirely possible his father was drafted as a young man, or even teenager, by a regime not all Japanese necessarily agreed with.
Zoanoids are genetically compelled to obey authority, to go fight and die in battle without questioning. The Japanese culturally were. They fought in the name of the Emperor, an exalted being who was said to have been descended from the gods themselves, but who, himself, played little part in the proceedings. His most aggressive and deadly ally was Nazi Germany, who idolized the Aryan ideal, and wanted to rule the world using a super-weapon. Although it may be going a bit far to equalize the Guyver with the atomic bomb.
Anyway, Sho is definitely the ordinary boy who says 'Hell no, I won't go'. Usually such an effort is punished, but he has the power to resist... it is stated repeatedly that the aspect of the Guyver the Creators feared most was the power to refuse orders. "Out of control".
If Sho is some kind of chosen one, if he is innately special, that weakens that message. But compare him to some of the others in the story. Murakami was a daring journalist who travelled to the ends of the Earth to pursue a story. Makishima had a tragic and bizarre back story which forged him into a sort of Übermensch who would do anything to reach his goal. The Zoalords are by definition exceptional individuals, otherwise they would never have been chosen. Waferdenos isn't even human, he's a frickin' forest. And Archanfel himself is completely unique.
Set against this collection of super-people, the most normal and average person conceivable: a school boy. Not the head of the class, not even the gifted and quirky nerd... no. He even looks average. Sho represents the teeming masses who do not want to rule the world, but who simply want to live a life (with his female equivalent: Mizuki). It would seem all of the others would have wanted the Guyver for themselves... and he never would. But he did, through blind chance: another act of defiance, a test type Zoanoid who disobeyed orders and chose death by his own hand over becoming cannon fodder.
I wonder if Takaya considered having Malmud/ Melmoth/ Guinea Pig use the G-unit on himself. That would have been a different story...
And Mizuki, too. She was in the area, wasn't she? A mere changing of the angle of the blast could have landed the G-Unit in her lap, so to speak. That would have been a really different story...
Of course, there is a higher power that directed events: Takaya himself. But I don't think we should be looking to actual gods in the story. The only gods are the Creators.