I'm aware of just one "official" Hamas formulation of the slogan, via the 2017 charter as quoted below. Can you point to any others? We do have that quote from Khaled Meshaal as well, but one doesn't hear it so often.
Hamas’ 2017 charter states that in principle, it “rejects any alternative to the full and complete liberation of Palestine, from the river to the sea.” In a 2012 speech, Hamas leader Khaled Meshaal said, “Palestine is ours from the river to the sea and from the south to the north. There will be no concession on any inch of the land.”
Regarding the nicer-sounding variants that "nobody wants / aren't workable": That may be, but it is significant that the variant that most folks in their camp at least pretend to believe in (as an "aspiration") is at least nominally non-genocidal. And that the genuinely genocidal variants -- just aren't on display that often.
(Might get back to the other stuff you wrote later)