Here would be my own crazy rewrite where I try to change as little as possible.
Planet of Monsters
- The opening sequence is slightly different. Still show the historic attacks, but show a larva Mothra was in the midst of them and was battling several other monsters when all of them were nuked repeatedly, humanity thinking it was finally over in a conflict that cost much of North America.
- But this was just the first wave. More kaiju showed up shortly before the respective aliens did. That's when Godzilla appeared. Destruction ensued with Haruo as the sole survivor of an attack by Godzilla that occurred when he was just a baby. Years later, the few remaining humans launched into space, with a near-miss at the airport as we saw in the film. Notably, Godzilla seemed to look directly at a young Haruo.
- Much of the film proceeds as normal, but one reason Haro is followed is he's one of the very few to survive Godzilla twice.
- Additionally a reason they land in Japan is the global scans do pick up multiple kaiju and Japan is one of the few zones with very few. They can't detect Filius because it's established Godzilla is near impossible to track.
- Foreshadowing to the Hotua with one of the scout teams seeing patches of mundane plants with picked fruit, with a human-like footprint.
- During the scouting surveys, the Aratrum detects a kaiju making rapid movement to their location and it seems it's heading for the ground team (foreshadowing, it's not). But they can't get a signal through the atmosphere.
- In the midst of the plan to kill Filius, the other kaiju (let's say, Orga) arrives and Filius breaks off to attack it. The plan is adjusted to let them fight it out, then kill Filius while he's weakened. It succeeds, but a point is made when Filius looks at Haruo much like how Godzilla had.
- Filius is killed, Godzilla gets ticked and begins to attack (and did not proceed to get blocked by Shaq or any Shaq Fu).
- Right off the bat and continuing on, there is much more tension between the survivors and Hotua. For the sake of convenience I'm going to call Miana and Maina, Moll and Lora respectively just so it's easier to tell who's who with writing this. Moll saved Haruo in this one and she saves him from a Servum by pulling some scale dust off herself and throwing it on him. The Servum then ignore Haruo. One noted difference is the Hotua do not use nanometal.
- While hiding from Servum, Martin finds a fragment of nanometal in a cave.
- When they get to the Hotua village, several things are immediately obvious. Firstly, the plant life is decidedly 'mundane' and not the horrific forest of knives seen earlier. Secondly, despite no cover, there aren't any servum attacking. And thirdly, there is a gigantic egg or cocoon in the heart of the caverns; clear as day. When wondering aloud what it is, Haruo hears Metphis call it 'Mosura'.
- The Hotua aren't casting the survivors out, but they are very much not welcoming and are far more unnerving given none of them speak aloud but the survivors can feel their thoughts being probed. All of the Hotua are telepathic and use it extensively.
- Wondering just how these people live in this world, Haruo gets his answer when he sees from a cliff what appeared to be a sinkhole is actually one of Filius' footprints; showing it had walked right past the village and paid no attention to it. Moll or Lora could also be sighted on a gathering run completely ignored by the Servum, whereas rare mutations and smaller monsters are attacked.
- Paranoia and distrust sets in further when it's revealed 'Mosura' is actually Mothra and the Hotua are worshiping a "monster" and Lora notes how the elders are quite upset Godzilla is active and Filius, the 'Heir of Destruction' was killed.
- Unwelcome, the survivors go out to find the source of the Nanometal after Martin shows it to Galugu. They make it to Mechagodzilla city, which is still animate and active; doing operations like shooting down Servum. In eerie foreshadowing, Metphis sees a hotua skeleton being eaten by the nanometal.
- The initial plan is to just make a ship from the nanometal and bail, but it'll take time.
- Martin has some lab equipment made for him and runs some tests. First on, some dust from Moll and then on a piece of Orga. In a callback to how he did this in movie 1, it's revealed here the Hotua are indeed part Mothra; but curiously Orga has some DNA that doesn't match up to any Earthly lifeform, contradicting the notion the kaiju are purely mutants of native forms.
- In a change, Metphis actively supports the Buisaludo getting the city online. There is a debate, with some noting Godzilla is inactive and hasn't moved since they roused it. Opposed to leaving, the Buisaludo pitch to scrap the spaceship, arm the city and rebuild Mechagodzilla to destroy Mothra's egg before it hatches. Both because the egg is 'infecting' humanity and they best destroy it now before they have two active monsters to deal with.
- The warhawks win the debate and it causes some divides.
- Some of the themes are more highlighted, with Metphis remarking on the evolving nature of nanometal. It has, it seems, evolved from the Buisaludo's invention into their god in how they devote to it.
- Some that don't agree with the plan go to warn the Hotua as they're worried about them getting caught in the crossfire. As the railguns and Mechagodzilla are being rebuilt, Moll and Lora are informed and lead a prayer to the egg. Just as Mechagodzilla nears completion, Godzilla comes awake and immediately makes their way towards the city.
- More or less similar finale with Godzilla bulldozing their way into the city, but the harpoons and vultures are to mostly slow down and damage it while Mechagodzilla is created by cannibalizing the city. We get a proper fight which looks like a stalemate, forcing the nanometal to spread out and cannibalize more and more of the nearby matter to rebuild Mechagodzilla. This actively shows there would be no stopping it should Godzilla lose. The nanometal begins to threaten the Hotua and this spurs Haruo to use the vulture to shoot at the central computer. This gives Godzilla the opening to win.
- Movie ends with Yuko's death and the survivors being very hesitantly taken back to the Hotua, but are imprisoned.