As title says, if you have any ideas for new abilities you can share them here.

NEW:
Glowstone backpack that gives you dynamic lighting (which I assume is not built into your mod, but could work with other dynamic lighting mods). Recipe: 8 glowstone blocks around the backpack

Rabbit backpack that allows players to walk on powdered snow/permanent speed 1 (balanced by rabbits being very rare and hard to farm)? Recipe: 3 rabbit hide in v shape, 2 rabbit feet on bottom corners, and 3 rabbit meat along the top.

Cave Spider backpack that makes you immune to poison. Good for modded dungeons with lots of them

Slime backpack that makes players bounce and take only 25% fall damage. Recipe: 8 slime blocks around the backpack

Piglin pack that makes piglins neutral to you (as if you were wearing gold). Rarely dropped by piglin bartering, or this mechanic could be added to the gold backpack

Piglin Brute pack that makes both piglins and piglin brutes neutral. Rarely worn and dropped by piglin brutes.

Guardian backpack makes you immune to mining fatigue and not attacked by guardians (similar to how the ghast backpack works). Recipe: heart of the sea bottom middle, 4 prismarine shards middle and bottom sides, 3 prismarine crystals along the top

Shulker backpack gives you permanent resistance 1. Recipe: 8 shulker shells around the backpack

Totem backpack gives you the totem of undying effect when taking a fatal blow, but goes on a long cooldown of a few minecraft days. Recipe: 3 totems in a v shape, nether star top middle, and 4 gold ingots in the corners.

Herobrine backpack crackles with ominous energy hidden effect, rarely found in ancient city chests?

Warden backpack makes you emit no sounds or at least no vibrations. Gives you permanent resistance 1 and strength 1, but also darkness. Dropped by warden.

Bedrock backpack gives you resistance 4. Easter egg creative only item with no recipe.

CHANGES:
The bee pack is also not very good right now compared to many of the others. How about it also gives players regeneration when standing on a flower (be sure to include forge/flowers)

Skeleton pack should give a 50% chance to not consume any arrow even tipped/modded ones.

Emerald pack should require a villager pack in its crafting recipe (instead of the regular travelers one), and in exchange give you the hero of the village effect for better villager trades? The gifts you get from being hero of the village are not that good but can be useful in large amounts, but the villager pack requirement means you must at least have leveled up a librarian villager fully and paid a hefty price.

The wolf pack could automatically tame any nearby wild wolf. MAY YOUR DOG ARMY BECOME REALITY

Also, can all packs have a few slots for arrows, say in the bottom right? Currently they holds tools, water, can craft, but not hold arrows? To clarify, I mean slots that can be used, and would be consumed whenever you shot an arrow. Imagine a quiver.

for the hefty price of a netherite backpack, i suggest adding a secondary ability to it to make it worthwhile compared to keeping it as a diamond one, perhaps a larger pickup radius? (this is suggested in relation to the theory that netherite is magnetic, since it is the main material in a lodestone)

My idea is kinda two-fold. One change and an addition.

First, as much as I love the Squid backpack, it is such an incredibly powerful effect for the very little amount of effort required to make it. My main suggestion would be to change it's ability; make it give the effects of the Depth Strider (increases underwater movement speed) and/or Aqua Affinity (increases underwater mining speed) enchantments.

Second, a new pack, the Conduit backpack. It would give the Conduit Power effect, which is comparable to a combination of Water Breathing, Night Vision (only underwater), and Haste (only underwater). For the recipe, I'd suggest a conduit it the top middle slot, then a v of prismarine shards, and then in the left and right bottom slots prismarine crystals.