What I Want to See With Metroid & What Could Push a Metroid Game to 20 Million Units?

[Slownenberg]

Well I'd say Switch's user base alone will get MP4 to at least 5 million, even without the devs doing anything to try to make the series more popular.

In terms of your ideas:
Open world yes absolutely, I like the idea of having a less linear map, still of course with areas you need specific abilities to reach, and still with some areas that are linear puzzle or battle set pieces.
Don't agree with the adding towns/people or whatever. That goes against the whole Metroid plot so that wouldn't make sense and doesn't fit with Metroid.
Emergent gameplay would of course be welcome, though not sure how this would take shape.
A home for Samus...hard pass. No reason for this at all.
For storytelling I'd rather just have a really good intriguing story that mixes well with the gameplay.

Basically, yeah make the map more open (while keeping some areas inaccessible until powerups are attained) and any addition of emergent gameplay would be welcome but the rest are bad ideas for Metroid.

My pitch would be:
I'd say make the story something like having Samus chasing down enemy, planet hopping where each planet can offer a different environment. This would allow diverse natural environments as well as a mix of civilization environments. Like there could be planets that are composed of ruins, could be all forest environments, going through ice caves, an asteroid mining facility where you're going through tunnels and also the surface of the asteroid as well as abandoned mining buildings, a high tech city run by robots where get to explore interestingly designed robot buildings where you can say shoot out a window and grapple hook to another building and crash through a window and it could also include sci-fi vehicles to hop into, throw in a spaceship level, and so on. I feel like you could really make a grand story with all these environments and chasing down the enemy, while keeping the settings varied and providing some variety of gameplay, and giving the player a great sense of exploration going through all these different planets and whatnot. Make epic boss battles and diverse and really interesting enemy battles. Somehow make the story make sense even though you can go to pretty much any planet whenever you want after say the first one. And then of course market the hell out of it.