Overall very good points. Open world will make wonders for Metroid, but I'm sure the fandom isn't exactly expecting this. They seem to like the more tight design of Prime series, I guess the best way to good is indeed something like original Zelda, where you have a nice open world to explore and fight enemies while still having dungeons with tight level design and puzzle solving. Metroid is also sci fi based, so the open worldness can easily incorporate elements of other genres such as driving, flying/spaceships battle, essentially making the gameplay more varied. Needless to point that most of those options have to be optional as not everyone enjoy them. Freedom is gameplay allow players to choose what they find nice about a game and ignore whatever they find boring
I also like your idea for a non linear story, I would love something like Horizon, but with much less direct exposure and more focus on collecting. Let people collect the fragments of the story and watch them in a more optional way, you can even skip the story altogether if you don't care for it.
On top of that, make the classical Metroidvania backtrack looks more seamless. I don't dislike the idea of getting access to certain areas of the map only after unlocking some skills, but those areas would be more nice if they were mostly optional (optional but with high rewards). I can imagine some smaller dungeons scattered around the world that are fully accessible/explorable only after certain set of skills are unlocked, akin to shrines but looking more like Horizon's Facilities
Unfortunately not really feeling this will able to pull anything significantly bigger than 10 million regardless of the strategy used
Mostly cause Metroid isn't coming anytime soon. The development was essentially reseted in 2019, my safe bet for a game with a Metroid scope would be 2023, probably closer to the final moments of Switch's life
The IP doesn't have a flagship status to move an insane amount of software in launch, it would need to be based in a insanely great word of mouth and no matter how good word of mouth is, if a console is dying people will just ignore it and move forward
One way to put out 20 million would be make this game cross gen, or at least backwards compatible, making a remastered version a launch title for Switch sequel, then I can maybe see 20 million becoming here but still a crazy high expectation for an IP that never crossed 5 million copies, is Nintendo willing to taking the risk of have a game as costly as their biggest IPs even if this game has nowhere near the same sales potential? We have yet to see
