Before I offer my personal answer to that question, let me preface this by saying that I personally think a non-authoritarian Alternia seems to run counter to the trolls' very biology. Sure, the hemospectrum may be a lot more nuanced than real-world examples, but there is a clear hive-caste-system in their physiology; plentiful but low-ranking workers juxtaposed with fewer but longer-living upper classes. There is a fundamental inequality there that I think will be difficult for any troll society to truly counteract- especially since the differing lifespans, and therefore the amount of time each troll has to spend to advance their personal cause, is arguably the single biggest inequality between them!
I think it's telling that part of why Repiton in Vast Error falls under a very different governmental system than mainstream Alternia probably comes down to the simple fact that the degradation their planet and species is being confronted with has most likely leveled the playing field between the highbloods and the low from a pure-longevity standpoint. I've no clue how their take on the trolls differs from the 'main' batch of trolls beyond the things we can clearly tie into these past woes, mind you, but that feels like a significant contributing factor to me.
So what would non-authoritarian Alternia look like? Hard to say. We can't look to Beforus as an example here because- putting aside just how little we truly know about that setting- it is also authoritarian, even if Beforan!Feferi has a very different idea of what that means compared to the dystopic empire Her Imperious Condescension fostered. However, the fact that Gl'bgolyb is presumably not present in Beforus implies that such a sea monster is not necessary to propping up this imperial structure; the big sea monster was merely a tool to prevent anyone from interfering with The Condesce's Doc's designs.
In the event that the Sufferer, Summoner, or really any upstanding rebel succeeded in deposing the empire- or even just the trolls on Earth C learn from the mistakes of the past and strive to build a much more egalitarian system? I think that some fundamental sense of inequality will still remain in the low and highbloods, psychics and psionic powers aside. The traditional caste roles will probably get dismantled though; legislation will cease being a solely Tealblood thing, the Purplebloods are no longer forced to adhere to the Subjuggulator cult, etc., with only the chosen/volunteering Auxilliatrixes among the Jadebloods remaining true to their chosen role due to it being a fundamental part of their caste biology.
Governmental reform is not a quick or easy process, and there will be challenges- not just here but with population concerns, in providing equal opportunity between lowbloods and high, in properly reconciling the differences between all these castes and making each one feel heard and welcomed in the new, and likely many others that don't immediately come to mind. The only thing I can say for sure is this: that a non-authoritarian Alternia will be, by necessity, extremely different to the one we're acquainted with.
Oh no, not this dumb scepter again!