Oh my God anything but this. I was on board until this part. Why him. If anything, I'd argue the themes are a lot more important to each intentionally discrete era than any character. The Chaos Emeralds and their story, for example, bring a lot about unlimited power/mystic brings/things you shouldn't touch/past x future themes thay seem especially irrelevant in the boost games (they're there out of... inertia, mostly), but they are extremely important in the Adventure games (plus Sonic Battle!).