From my understanding Cari made OIAL with just a general idea of the story, with everything else he made up as he went. With Eternum there seems to be a more deliberate foundation given that he's mentioned on his official Discord that he already has all of the story beats outlined from beginning to end, with the only things he hadn't being the LI events as he likely wants to be flexible with that.
Point being, IMO there's little danger of a repeat of OIAL's epilogue given that he has a clearer idea as to where things are headed and all he has to do is to work his way up to that point. And as
Dylan741 had said (which I am in perfect agreement with), this game seems to be Cari's "Fate/Stay Night," where he basically solidifies and lays out the actual lore and rules of his universe instead of just making it up as he went for the most part like he did in OIAL.