Well, that was an easy fix, like I said, there were multiple ways they could have gone around it. The reason I didn't suggest side characters giving them Ridewatches was because it feels very lackluster. Like, they bothered enough to have Fourze show up for a bit, to de-transform into a fill-in for Gentarou, yet couldn't be bothered to do the same for the other characters.
I understand the need to like, try other creative ideas, I think it's a nice thing to do (having side characters showing up all the time to hand out Ridewatches in place of the main character can get repetitive and boring), but like, you gotta decide which ones best compliment the story of Zi-O, and doesn't break the lore of the previous shows. In Hibiki's case, it would just seem like someone else becoming Hibiki outside of anyone we know of should have been the best option. I mean, it's also a metaphorical admission from the writer right, that "sorry, we fucked up Hibiki and pretended to be him".
Like, the way I see it, I had a big problem with how Kiriya was sitting there and Sougo tells him "it doesn't matter if you weren't the real Hibiki, to Tsutomu, you were." because to me, that sounds like the writer was kind of saying "it doesn't matter that the second half of Hibiki sucked and wasn't really Hibiki anymore, because to plenty of other kids who had no idea about writing in general or the problems the staff had, it was a great show and it is still Hibiki!" It's like, I just saw Kiriya as a big projection from whoever was writing the episode, completely drowned in their subjective experience and validating that by finally having Kiriya become Hibiki, despite the fact that if he ever takes up the mantle, it means Hibiki failed as a mentor.
Like man, talk about cutting the development AND validating the fact that Kiriya being Hibiki means they didn't understand the philosophy behind the first half of Hibiki at all, because becoming Hibiki meant embodying the philosophy as well.
But, outside of the Hibiki stuff though, I really felt like they did Yaguruma dirty this episode. He's just going to be constantly stuck in "I'm in Hell" phase for like however long that remains an iconic thing.