Someone put a lot of effort into addressing the common complaint that the entire Metroid series isn’t exactly like Super Metroid, with different maps.

You know what a Metroid II remake would really need? Complex lighting. And lack thereof.

Lack of ambient lighting, a lot of the time. You’d get some from lava, from certain bioluminescent materials, and whatnot. Maybe some areas would be brightly lit. Mostly, though, and at times exclusively, you’d be relying on a certain tapering bubble of light around Samus. Outside of that you’d get a vague hint of shapes and motion. This would also give the game a somewhat monochrome appearance.

Maybe the more injured Samus is, the smaller the window or the dimmer the light, or the more flickery.

Heck, maybe phaser shots would set things on fire, creating light and attracting/distracting certain monsters.

Maybe, instead of a map, a way of marking the terrain. So you’d know if you’d been somewhere. Like, if the spider ball were to leave a faint residue behind…

Shepard: You could even have upgrades that enhance how much light Samus gives off, as an extra bonus.
Like maybe your gun shots are a little more sparkly now.

Eric-Jon: I can see an argument for adding the charge shot.
Just hold the charge to light the room, pretty much.

Shepard: Try to tune it so that Samus’s ambient light increases as the environmental light decreases.
So at the beginning you’ve got all these fungi and lava pits and glowbugs.
And by the end it’s just… a dead pit.
Maybe the occasional nigh-dead Chozo lamp.

Eric-Jon: I like how a lot of the natural lighting will be a deep, threatening red.
From all the lava.

Shepard: Mmm.

Eric-Jon: A lot of the game, where there’s color, it will seem tinted.
Oh heck. And light would generally just show the surface of things. So outside a certain number of pixels (one “block” or so), walls would be flat black.

Shepard: Yeah.

Eric-Jon: A narrow, well-lit corridor would still leave half the screen dark.
Creating a sort of letterboxed, managed feeling to the space.

Shepard: I wonder how that would look if you had the rare, fully-lit-even-penetrating-the-tiles room, for Chozo Artifact rooms.
I get the feeling players would want to just chill out in those rooms.

Eric-Jon: That would seem comparably tranquil, wouldn’t it. especially if the light were to have a sort of ethereal, light blue cast to it.

Eric-Jon: I want to play this now.
Heck, this sounds closer to what Metroid should be doing in general.

Shepard: It is warm inside the power suit.
Everywhere else is cold.

Eric-Jon: The third game set too much of a template for laying everything out in front of you like a videogame. Here’s this kind of tile, which needs this kind of key to break. You need this to get through here. Everything laid out clearly; you just have to go through the motions. All very rational. Of course, it’s a lot less obnoxious about this than other games that followed (and preceded it). Still, Metroid shouldn’t be an action puzzle game. It’s supposed to be mysterious, oppressive, anxious, and a little wonderful.
The first two games have this.
Fusion does, a little, in its completely different way.
Prime does, pretty much. The first one.

Shepard: It turned “do it because I said so” into the actual story.

To add to earlier ideas: surfaces glisten. So (depending on the potency of a light source and the reflectivity of a material) to things just outside the range of full lighting, you’d still get some faint one-pixel-wide reflection off any surface parallel to the light source, partially outlining an otherwise black mass. Which would be incredible if there were several living things around the edges of the screen.

Combine this with the business about spider balls leaving residue, and there’s a lot of complex stuff going on with edges.

Maybe an infrared visor upgrade, that you can toggle. Danger of flaring sometimes, especially when you’re shooting. When exploring and travelling, generally speeds things up.