The oxygen-reservoir, and the usage off-tether, is in my opinion, too short. To be dependent on either tether or oxygen minerals found in the ground is absolutely fine, and by all means, there are valid reasons to be dependent on it.
However, the on-pack standalone oxygen-reservoir should last for more than 45 seconds to a minute, and rather last 2-3 minutes. I've found myself many times in a hole i dug to avoid the passing storm, only to have my oxygen run out and die. And to have lots of oxygen-tank in your backpack takes up a lot of space as well, specially if you started a fresh save. In which leads me to;
Backpack storage, i don't know if you have anything planned to expand the storage on it, or make it so we could have customised backpacks, more than it already is customisation-able , but it would be nice to be able to increase storage-slots with additions, that's all
Map. A map would prove very helpful of you're on a roadtrip with your 4x4 heavy duty off-road rover\truck, or just walk, including underground. Atleast died 20 times due to getting lost and lose sight of my tether, so a map, generated from the topography of the planet, would be quite helpful.
Have in mind, i do not know if these suggestions, or rather ideas, is in your plans or not, but this is just my penny for thought.
Thank you, and good luck developing!
These are suggestions based on my own personal opinions, un-biased of any third-party or any other form of pressure!
(I've been burnt before throwing ideas around, so i'll just make sure)