I certainly agree that Yuzu would fit right in with any J-Pop star, I could definitely see him as an idol star! I think there was even a controversy around the end of the 2018 Olympics where a Japanese idol in a Korean group (I think it was one in Iz*One?) where she had posted a photos of Yuzu on her Instagram and that got some of her fans mad (pretty sure she was saying he was handsome and supported him during the Olympics). Dumb controversy, but clearly some idols are aware of Yuzu (and his handsomeness)
As for his SP for the Olympics I think it's very likely he will be convinced to use piano music because that's what the ISU and American media has pigeonholed him for. If he does a more rock/modern program he won't get as high marks since it'll be seen as "copying Nathan" or "outside his wheelhouse". I really hope he just says f**k it, and does LGC. That program is so fast, such an audience pleaser, plus, if he does go for the 4A I think that program has the best axel punch!
On the third point I do not think Yuzu will light the cauldron (if the Olympics still go on). Usually it is an athlete, famous for a summer sport, that lights the cauldron for the summer Olympics. Think in 2018 with Yuna Kim lighting the cauldron, she brought the Winter Olympics to Korea. But I do think Yuzu could be the final torch runner who hands it off to whoever lights the cauldron. I think there's a good argument that Yuzu's success at the Winter Games led to more Olympic excitement for Japan (unfortunately not with COVID but still...) In some ways I do think Yuzu's popularity will help smooth some areas over, but really, the Olympics are going to be a mess this year.