I’ve always wanted a Monster Island park simulator. Something akin to JP: Operation Genesis or the upcoming JP: Evolution, but without the customer management aspect (or you know what, maybe that could work too). You basically manage the island’s infrastructure, take care of the monsters and prevent them from escaping, and as you progress you get access to newly captured kaiju. Like in both the JP games, you get to control vehicles so you can explore the island from a human or airborne perspective, although normal gameplay would be the ‘god’s Eye’ view typical of the genre. Maybe there could even be a combat mini game where you capture new kaiju, or pacify rampaging ones on the island. Kaiju not adequately cared for go into rampage mode, where they wreck infrastructure, tangle with other kaiju, and maybe even escape. Other stuff like weather or (just for giggles) alien mind control plots could factor in as well.
This is actually the best idea in this thread to date