The only sort of revolution I can think of working in that situation would be one of the suppressed and cowed mages who are afraid of hiding trying to rise up against the government that oppressed them, essentially leading to a second war like the one that caused such fear in the first place. Of course, the two could always tie in well together or that exact reason - unlocking G's powers would increase the number of mages and their power, and necessitate a lot of travel and searching to meet up with other mages. I'm still a huge fan of the ethical side of things when it comes to his motivation, though. Maybe opening the locks requires some sort of morally questionable ritual, such as a human sacrifice? Or maybe just for the final lock, as a big twist right towards the end. That would be talking waaaay down he road, of course.
I was going to suggest that they try and find Mec a teacher at some point or something too, to help him learn the scope of his powers and better control them. Their ignorance of G and his voice could prove an interesting twist if Mec learns that it's not normal for all mages to hear him like that. Perhaps G alone is already enough to fill the role of a teacher, though, which would make it somewhat unnecessary.
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