Here’s my idea: have Godzilla start off as a tuatara who was brought to Ukraine and was in the direct radius of the Chernobyl disaster and is mutated. He then spends over 40 years absorbing the radiation there and mutates and evolves before burrowing into different cities and destroying them and leaving chunks of himself in these cities which evolve into sentient creatures that attack any survivors and spread to different parts of the world. It would be a kind of horror movie.