Why is there no territory with a Reed Richards in it? This is a world made by Doom.
Then you wonder why Doom wouldn't have a few versions of Reed around to gloat at, pointing out how it was Doom, not Reed, who saved everyone. And then you remember every time Doom thought he had the upper hand and Reed turned the tables. Doom has finally put the satisfaction of victory over his petty need to gloat.
This could probably explain why there's no Squirrel Girl in Battleworld so far.
Made a plot point in #4: Doom is terrified of him. Turns out he has spent years looking in every kingdom for some version of Reed, unsuccessfully. That Reed is both alive and also has nothing to lose gives even God Emperor Doom pause.
In the Post-Secret Wars Spider Gwen series, we meet another Reed Richards, this one a young black kid. So, either Doom never found him because he never considered that alternate universe Reeds might be of a different race and the kid was savvy enough to keep his head down (figuratively), or he was part of the "dreams" Franklin used to recreate the worlds after the fact.
In Hickman's run on Fantastic Four there was a multiversal Council of Reeds who got murdered by some undead Celestials, which could lead to a shortage of Reed Richards' too.
Showing Doom's face makes sense. For years, we've thought of Doom as a tyrant, a monster, and his face was supposed to be so malformed that we, the reader, could never be allowed to see it, that our own imagination would conjure up the most unspeakable of horrors. And as a villain, that was fitting. Here, however, Doom is something we've never seen from him before. Vulnerable. He has done the one thing he always set out to do, basically become a God. And we're told he's been doing it for eight years. And he now has doubts, concerns, uncertainty. He saved pieces of the multiverse and cobbled them together as a world, and is now the overseer and protector of all that remains of reality. And the image crafted for Victor Von Doom's face is scarred, as we've been told, and it's as damaged as Doom himself. But it is also human, not monstrous, and the artist did an excellent job at showing us a damaged person who is now, as we see him, also just a bit pitiable. This is not Doom seething with rage and cursing the name of Reed Richards as he dons his mask in shadows. This is a Doom who wonders if perhaps he is not the single flaw in his hodge podge world.
The complete lack of Reed Richards' on the Battleworld before the arrival of Reeds from 616 and 1610 is justified. All inhabitants of the Battleworld are the people present at the incursion points during their Earth deaths. However, Hickman himself previously established in his run on the Fantastic Four that the vast majority of Reeds in the Multiverse have formed an Interdimensional Council of Reeds outside of normal space and time, the majority of who were killed after the Reed from 616 joined. This still poses the question of why there were no Reeds to be found, considering numerous other deceased characters have been seen alive on Battleworld.
Those characters are only around because they're parallel counterparts.
Another component of the Time Runs Out prologue: when Namor and the Cabal show up on an Earth to kill it, Namor hunts down the Reeds and kills them first. This is also partially why Reeds (and Dooms) are so rare. They've been systematically removed from the Multiverse and are less probable to end up on Battleworld because of it.
Many readers have noted that Doom's personality seems to vary wildly in the tie-in books from what Hickman is establishing in the main series. However this is not a case of Depending on the Writer: Doom as presented in the different tie-in books is how the citizens of the various domains perceive Doom, as lowly mortals. Just as how different religions have differing views of God in the real world, thus do Doom's subjects all have different views of Doom. Doom's actions in the main book are what actually happens. Doom's actions in the tie-ins are how his subjects interpret what happens.
Reed restoring Doom's face might seem an odd thing for him to do, given that Doom had outright stolen his family. However, it's perfectly in keeping with the speech that Reed gives Sue about learning to let go.
It also fits in with his claim that he could make a better world. For all of Doom's power, he could not even heal his own face. Reed given the same power, could. He confirmed by doing that, he was better than him. And not just by intelligence or creativity - He had a better character than him: He could've easily made him disappear from all of existence for what he did, but he didn't.
Every X-Men, X-Factor, New Mutants, and Excalibur member who were actually there and participated in the original Inferno all appear somewhere in the Secret Wars: Inferno series. Wolverine is the only one who was there before, but now is absolutely nowhere in the Secret Wars revisit to Inferno. The Secret Wars Journals series features the Wolverine from the Inferno domain as having been sent away to another domain.
In the final issue of Spider-Verse, Spider-Ham tells the others that he discovered that he could be hit really hard and not be hurt at all. All fine and dandy. Except, how did he come by this bit of information? Bear in mind, he was staying with Norman Osborne at the time, and we first met him in a hospital bed.
In issue #6 of the main series, we get Battleworld's Sue recounting her meeting Doom for the first time. Valeria and Franklin hadn't been born yet. So in this version of reality, Franklin and Val might actually be Doom and Sue's children. Let that sink in for a moment.
Confirmed by the Runaways tie-in, in which Val is the Big Bad.