Imagine one of your favorite games, then reverse it's ESRB rating
Then, make any preferred modifications to the game to play around the gimmick.
[spoiler]for anybody who's confused: if the game you picked is E or E +10, then it is now M and needs a proper amount of gore, profanity, vulgarity and whatnot to make it so. If your game is M or T, then it is now E or E +10, and it needs to be toned down enough for kids to play[/spoiler]
My first game is an M rated survival horror Pikmin game. The premise is very sinilar to the first game; crash on alien planet, yadda yadda, except this time, the Captain launches an escape pod crashes a far distance away from their ship. This means that the Captain does not have the luxury of flying into space at night to escape the nocturnal creatures. And, just like in the original, the Captain coincidentally finds their engine on day 1.
The gameplay would consist of two phases: the day and the night phase. The day phase is pretty much exactly what we have in pikmin today: killing creatures and growing more pikmin, exploring around, building bridges and knocking down walls, gathering parts or treasure or fruit or whatever. This daytime phase would be much shorter than the previous games because the Captain has to sleep. Then, at the end of the day phase, you can choose to keep some of your pikmin with you for the night, and put up the rest. The Onion is going to fly up in the air at night, keeping your Pikmin reserves safe. Keep in mind, you have to cart around the engine to your ship the whole game, which woukd discourage players from taking all their pikmin out at night.
The night phase is the bulk of the game and where the difficulty come to life. You can still kill other creatures at night with you pikmin and continue daytime activites as well, but it's going to be a lot harder. There are many more creatures and most of them are going to be the bigger, tankier, more dangerous stuff. Also, you'll have to do it in the dark, where you can't hardly see and the monsters can. Also, you won't get any rewards for killing at night because the corpse will rot before the Onion arrives back down in the morning anyway. The purpose of bringing pikmin at night is one of misdirection and distraction, sacraficing a few to save the Captain. At the end of the night phase, the Captain and however many Pikmin survived the night will plop down to sleep wherever you are, and then the game will reload to the day phase. You will start the next day phase wherever you ended up after the night.
The engine plays a pretty big role because, to beat the game, you have to bring it to your ship. So, not only do you have to have a few pikmin carrying it around all the time, but you also have to figure out what to do with it at night. One of the daytime objectives would be hiding it under a leaf, but, if you hide it too close to a Bulborb's stompimg grounds, then it will find it and eat it. Then you'll have to hunt down the Bulborb and kill it to release your engine. Also, certain critters will build back walls and break down bridges, so if you could possibly lock yourself away from the engine inadvertently. You could have pikmin carry your engine with you at night, but you'd be much slower. You could also kill the critters pretty easily if you get to the bridge or wall at the right time, so if you really needed a certain pathway open, you could guard that passage at night.
There will be multiple areas, but, unlike the other Pikmin games, you can't fly to them. So, while the maps will still be open and explorative, it will all flow in ome general direction. The Onion will always land in the same spot (which can be accesed from any part of the map, so you can't lock yourself away from the Onion at night) for each zone. Once you get to a new zone, you can signal to your Onion to land there instead, whichbwill define when you've gotten to a new level.
And maybe the game would be played entirely in first-person. Or maybe just the night phase. Or maybe not at all, idk.
Now it's your turn to come up with something! You don't have to put as much detail into it as i did (i kinda went full nerd there), but it'll be cool to see y'all's ideas.