[Increased resource drop chance mutations]

Towards the end game, you need to kill a lot of enemies for construction, smoothies, armour repair etc..
When I want to kill higher tier enemies with lots of health, I still feel forced to go back to kill A LOT of lower tier enemies for basic resources such as gas sacks and dust mites for arrows, mosquitos for their abdomens etc..
These mutations are to help acquire lower tier materials for basic needs, when you want to focus on higher tier progression.

Scavenger Mutation Increased insect drops
Your time in the haze has made you an expert at disassembling fallen enemies
There is a **10** / **25** / **50 percent** chance that bugs will **drop double their resources.**

This mutation is levelled up by disassembling or looting dead insects in the haze.

Plunderer Mutation Increased chance of finding buried treasure
Discovering buried treasure has given you a keen eye, no resources go unnoticed
There is an increased chance that treasure will spawn.
This mutation is levelled up by digging up treasure.

Carver Mutation Increased chance of getting more drops from smashed resource nodes
You learned a thing or two about breaking resources
By breaking clay, quartzite, salt, spider sacks etc.. there is a 50% chance for them to drop 1-2, 1-3, 2-4 extra materials.
This mutation is levelled up by breaking tier 2 resource nodes.

**Mutation tiers**
Tier level 1/2/3/4/... of the mutation would affect the tier of the affected resource node.
so
Tier 1 = more rocks
Tier 2 = more salt
Tier 3 = more wood splinters
etc..

[[Suggestion] Bestiary]

Ailments, Showing it's resistance to debuffs and

Materials Showing the different drops that it can drop.

[[Suggestion] Bestiary]

I ABSOLUTELY LOVE the Monster Hunter bestiary, and I think it can be a source of good inspiration for the grounded bestiary.
As a bonus, all monsters are hand drawn art which make it so much better.
It has four tabs :
Ecology, showing you the general information about the monster and its environment

Physiology, showing you the monsters weaknesses and attack patterns

[Elevator In Grounded]

Something like this would be awesome to build on the outside of buildings, or bring resources up the sides of cliffs and buildings.

 

[Gliders]

Hang gliders can definitely be a step up from the current ziplines, ziplines force you to go from A to B and are expensive to setup, a hang glider would use up durability. Just like ziplines, the hang gliders would have a constant rate of descent that changes with the quality of the glider.

lvl 1 -> Dandelion fluff, usefull for breaking a big fall
lvl 2 -> The drink umbrella, character dangles, transported mainly by wind currents, a bit like Mary Poppins, it is somewhat controllable.

lvl 3 -> Butterfly wing hang glider that allows you to travel a lot of distance and is controllable

[Friends access multiplayer without host]

There are two suggestions here:

Company Hosted

Just like "Minecraft Realms" where you pay a monthly subscription to the company, the company will keep a server open for you to play on with your friends.

Self Hosting
Terraria, Rust, Minecraft and other openworld exploratory games distribute a server.jar or service that can be run mostly on linux for people that want to self-host a server.

It allows the host to run it as a service in the background on a linux device that is on 24/7 so they don't actually have to launch the game on their PC every time to enable others to connect to the server.
 

[Mounts]

I absolutely love the comparison to "unlocking of car via fob" XD

Mounts and the ability to fly seem to be a very end game goal to me since I just unlocked ziplines and am happy with that progression where a lot of the game is in going from A to B and exploring the world.

Fireflies would be the perfect tool to navigate the world in the dark, and definitely a progression tool to reach end game challenges and content. The ability to fly will render a lot of content obsolete. So it would be limiting if all future content of this game had to take flying into account. This would render challenges like "How do I get to the birdbath?" obsolete, just fly there, boom, hedge navigation challenges cheesed.  So I'm all for this being true end game content (Maybe can come in usefull to navigate the woods treetops?).

Land mounts seem very fun.

How would we get the creatures to become mounts?

I've thought of a few steps that could work into subduing the creatures to turn them into a mount.
Bringing their health all the way down, knoocking them out, trapping them or feeding them special food.