The thing is, and maybe Hiyori hasn't thought this through, is that I feel like she isn't actually rejecting the idea of HEAVEN there necessarily.
I think there's been a conflation of HEAVENs with "isekai power fantasy as portrayed by modern anime" which makes some sense because the only one we've fully explored is ALO and Sugou more or less perfectly encapsulated that mindset. But we've seen repeatedly throughout GGO that Hiyori has to stop and reassess that it's
different here. Certainly there's still something of a power fantasy argument to be made here in "being the strongest" but it's a very different flavor.
I actually think SAO is somewhat instructive here especially given how in-quest Kayaba handed the reins over to Kirito there. Now, being both a prototype HEAVEN and having to work within the constraints that it was initially built up with Kayaba as Chosen I don't think it's unreasonable to think that later-SAO was more geared towards Kirito's desire and became, at least to his perspective (and divorcing it from the rest of the franchise for a moment) something more akin to a shonen anime - challenging boss fights, nakama, a love interest in Asuna all with a Big Bad at the top to take down in Kayaba. But it still had tragedy and loss for him - the presence of those things doesn't disqualify a world from being a HEAVEN if the Chosen values those things.
I guess what I'm getting at here is that I don't think Hiyori asserting she wants to confront and accept herself is
necessarily at odds with HEAVENs as Kayaba sees/intends them. It isn't too hard for me to imagine a Hiyori who says this to Kayaba to be presented with a HEAVEN where she is occasionally presented with challenges/obstructions to overcome/become introspective. It probably looks
similar to real life - albeit distorted, in a protagonist-centered way. To put it in less serious/more comedic terms it would almost be like a slice-of-life/drama anime with Hiyori cast as the protagonist who things just happen to at a weirdly high rate.
Not that there's anything wrong with that - I think it'd be interesting for Hiyori to state her vehement opposition to HEAVENs only for Kayaba to analyze her statement and either realize or optionally point out "yeah, I can work with that. you're not really stating an opposition to the concept, you just loathe some of the more cartoonish/grotesque fantasies held by others. but that's why everyone will receive their own HEAVEN so there need be no zero-sum contest between all these desires."
Or maybe I've just lost the plot entirely.
