So, yeah, things actually became a bit more clear now.
I definitely agree with keeping as much as possible self-contained within the game.
There's one issue with this though, most of the things I plan to possibly put inside locked zips can not be put inside the actual game. (it's not images, audio, video or text)
So I don't really have much of a choice other that zips for those specific things.
But for anything that is one of the things mentioned above, those can be put inside the actual game and I will try to find a good way to do this, if I decide to include any of these things.
As for the atmosphere stuff, I've only scratched the surface of what I actually want the atmosphere to be like, hopefully I can fully realize this with time. And yes, most of the super metroid things you listed are actually a big inspiration for atmosphere, mostly the tourian lift corridor and maridia glass tube stuff.
And about the internet, yeah, there is definitely nothing I can do, even if everything was included inside the actual game there will still be videos of how to do this and that, videos showing all the unlocked achievement stuff, and most likely even unpacked game files available somewhere. (depending on game popularity)
And I know *of* Hyper Light Drifter, the gameplay just didn't look like my type of game so I didn't really care that much, so I don't know, I probably won't look that deep into it.
So yeah, I basically agree with everything, it's just hard to actually make things happen the way you want in-game, and I've got so many planned things (definitely too many) so we'll just have to see what happens with time.
I appreciate the feedback / suggestions as it has actually helped me think of things to do / add, so thanks for that. ;)