well, if we're going for 'space suit/pressure suit/combat armor' then segmented plates could add a neat look

and maybe multifunction visors? bolting on a new visor could be some permanent upgrade to your FACE VULNERABILITY score and also a vision/etc upgrade

GIANT METAL PLATE
Makes you almost invulnerable towards enemy fire but severly impairs your vision.

Hmm. Maybe you could change your helmet based on the situation to better suit your needs, and there would be several different kinds of them hidden around the planet. Then you could make some sort of "Collect them all!" challenge or something.

I was thinking there would be 2 inventories, one for clothing and one (handled by whatever you're storing your stuff in) for consumables and other items.
That way, we can have old packs etc from dead crew/empire members actually mean something.

ELABORATION: Any "storage" type item has x slots in it. those slots can have other items put into them (guns, explosives, ammo, or even upgrades like suits or helmets) and are held by them item. You have direct access to whatever items are in your equipped pack, and access via interaction (a press A to talk type affair) to non-equipped containers (for storage crates/chests or stealing ammo from dead enemies), either moving stuff into your inventory or just onto the ground (in case you want to scatter their grenades around or whatever).
Your equipped items don't contribute towards filling your storage space (you don't wear your tshirt while it's inside your backpack) but do take up whatever slot they require and add to your weight just as any other item would (impeding jumping height, jetpack effectiveness, and walking speed, as well as increasing fall damage taken). You can wear anything at any time assuming you have a free slot, and it should change your appearance in game (the game should give as much feedback as possible without becoming overcomplicated).
Slots for equipment would be:

SUIT - what spacesuit you're wearing, maybe you can get better ones that do more stuff or protect you from xyz danger. Heck, maybe you can get one that does very little extra but has a better O2 storage system letting you dive deeper in water.
ARMOUR - what you're wearing over your suit to prevent bullets from ♥♥♥♥ you up. Can be field, plate, or both. I think a bullet should do about 70% of the player's health with a body shot if you're not wearing armour and the default suit, you shouldn't feel powerful when under-equipped (you're uh, a space pilot, not a muscleman soldier).
HELMET - armour for your head, goes over your suit helmet. This is your critical defense, each hit will have some chance of critical damage (sharp-aiming will raise this chance) and criticals do damage to the head. It'd be silly to do physical headshot detection when the head is 1/3 of the player sprite, but maybe it'll work better that way. Anyway, yeah, cover your head with a helmet.
BOOTS - A dedicated rocket-jump system comes default, but maybe there's boots that let you jump on enemies heads like mario or let you hover-jump without using your jet or something. Who knows?
JET - Your jetpack, with a limited fuel tank that "recharges" using any organic matter taken in by modules attached to your feet (ie only when you're on the ground). Can be upgraded to last longer or shoot heaps of really hot offensive flames or whatever else.
PACK - what you're using for storage.

The idea behind this game is to encourage exploration and tell a story, not to be an action shooter (though there's elements of that in there, especially towards the end of the game when the player has a lot of items and ammo). Mission logs and interesting caves come before giant rocket launchers and ACHIEVEMENT UNLOCKED to me.

You could probably justify the jetpack being limited a lot less obtusely.
Examples:
Based on an electrical system that relies on capacitors which must recharge.
Jets overheat quickly and the cooling system can only operate whilst relatively still (due to sensitive, fragile components).
The fuel is sourced from a smaller tank which primes the fuel. The fuel <takes a long time to be piped into the tank/be primed> and cannot <pipe/prime> <in heavy motion/while running> lest explosions occur.

Have limited fuel that you can buy from a shop or find in tanks/from enemies, and make it overheat if you use it too much.

Uh, there is no shop dude, you're on an alien planet and your ship's broken.

With the jet, it recharges while you're on the ground, not while completely still. I just need to prevent players from exploiting it and escaping the map, I'm not fussed about the explanation but it was better than "from the air" as that could be done while flying. I agree that I elaborated badly, though :/

I've already made an image splitter and a datafile maker for my own project, so perhaps nobody would have to do those boring things.

Wonderful! Though, I'm not sure how much splitting up of images we'll need to do for this, I'll do animation with quads so we can keep the sprites in one sheet for objects ('ray!) and the levels only have like 4 layers anyway.

So will this have the potential to mod openly and in-game easily or will there be restrictions and limitations to it?

Honestly, no idea. It's a feature I'd love, and it's possible, but I'll likely hard-code everything for a while. It's definitely a possibility though, but don't expect anywhere near the verbosity of CC modding. Scenes would probably be the most interesting to do unless we go whole hog and have an ecosystem that interacts with itself etc etc.

also:

whee shitty logo is shitty

Pink and bright blue flames from the jetpack?

EXILE was created on the 70's, so it's gotta be PSYCHEDELIC.

Indeed. All the particle colours in the game were brightly coloured, I figured I'd play on that with flames and maybe some explosions, while keeping it semi-sensible. It also means it isn't using any conventional earth fuel (or at least, it's had some crazy pyrotechnics development done if it is ) so I can toy around with values and not cop realism flak. The red on the jetpack indicates the jetpack's level btw, not sure what colour ramp I'll do but I prefer visual changes to having to check stat pages.

Obviously, there's high levels of copper and magnesium in the soil, leading to unusual pyrotechnic effects.