Wanted to talk about this for a second because I didn’t think about this until recently, and it was far too late to add it to my pikmin team-up picture.
Nintendo seems to always change what yellow Pikmin, specifically, are capable of. Bomb rocks in 1, electrical immunity in 2, good diggers in 3. So, for Pikmin 4, what if electrically/light charged yellow Pikmin could glow in the dark? On top of electricity acting as nectar for the yellows, it could also light up their bodies for a small while - the flowers being the brightest part, as the glow would slowly drain from the feet upwards an the flowers would be the last to go out - which would make them invaluable in dark caves without any light sources and perhaps even night cycles, keeping tender-eyed enemies away and protecting you from beasts that hate bright things. Pikmin is already an inadvertently scary game, and this could just amp up (no pun intended) the suspense to eleven.
We’ve already seen how their flowers can light up when electrified courtesy of the Pikmin shorts, so I think, at the very least, it could be a somewhat innovative idea. And whichever captain
I also think it should follow the number sequence, increasing the captains by one, and be 4 player (Pikmin 4, 4 captains, 4 players) but only if you have 4 Switches.
To prevent things from being too confusing, one of the captains is stuck on the planet and has to survive the night, with whatever Pikmin you may have left behind or left buried, while the other three quest to find him or her. That would increase the Pikmin making strategy, prevent the timer from becoming useless, and prevent unnecessary losses just because a few Pikmin may not have been whistled in time - of course, you’d have to save these quickly before they get devoured.
And perhaps the plot of the game could be Olimar taking his family to visit the Pikmin, only to discover that the planet is undergoing an extreme environmental crisis and they need to work together with the Pikmin to save it.