New game mode without free oxygen

It breaks immersion when you can easily build everywhere and even in the most hostile enviorments you can quickly setup a safe place with little effort - and it no longer appear as hostile. Building in the deep should take a little more effort. On top unlocking the tedpole brings in another level of safety to exploring.

Furthermore it is a bit weird that once we build a base and have a tedpole oxygen becomes suddently only a minor nuisence whearas it is a very noticable gameplay aspect before. This transition would feel better if it was more gradual. Because this massively impacts how easy exploration is - suddenty the world appears much smaller since most of it becomes so easily accessible!

I don’t want to suggest to change the normal game mode, but since we have game modes with more planned, why not make a new one focused on harder survial where oxygen is not free. Instead bases and vehicles would get a variety of dedicated modules and mods to deal with it:

• bases about 50m below the surface could use a simple snorkel system to passively provide oxygen (even without power)
• there would be various other options for bases to get oxygen, including a mid game oxygen generator (electrolysis from water), generator from some organic materials and also options to tap nearby fauna (external modul; similar to energy tubine) and so on.
• there are air tanks and rebreathers as personal equipment and bigger variants should exist for bases and vehices.
• for bases the interior volume would itself work as an oxygen tank, but buildable tanks would greatly expand that.
• the basic tedpole should start with a air tank capacity of 5 minutes.
• bases and vehicles only consume oxygen when a player is inside. oxygen consumption would grow with player number inside.

I am not sure if I agree with all of this, but oxygen surely needs to be a bigger nuisance in early game. In SN1, we were placing pipes to get air down from the surface while we have virtually infinite supply in SN2.

I can see something like this working. https://subnautica2.nolt.io/10319

How about having oxygen production requirements depending on base size/volume? This way, bigger bases would automatically require more power to run air pumps from the surface etc.
An alternative could be a craftable attachment to nearby oxygen tunics or spires for supplying the base Thgis would allow for deeper bases where pumping from the surface is no longer viable.
Last option would be electrolytic oxygen production.