Now that airtightness is officially done, I'd like to suggest radiation generation for reactors and other sources, it could be the same effects as being in an oxygen-less environment and would require players to plan where to build reactors. Something like this:
- Radiation would have something like a falloff on open environments, but in enclosed rooms it would fill the whole room with rads;
- Add special type of vents that have rad filters on it, which will need to be changed every few hours;
- Rooms without filter vents will gradually accumulate radiation unless a door is opened or room is depressurized;
- If normal vents are used to depressurize a irradiated room, then all the oxygen in connected tanks will be irradiated;
- If a door to an irradiated room is open, the radiation will spread to nearby rooms (again, falloff);
- Radiation cause damage to living entities (wolfs, players and spiders*), which is increased by the rad levels in the environment (entering a 100% irradiated room would be fatal, and a 10% room would cause normal suffocation damage);
- O2 Filter blocks, just like O2/H2 generators, but use oxygen + energy (filter?) to generate clean oxygen (maybe at a 2/3 rate);
- Filter item which can be made at assembler and has % levels (like canisters), being possible to disassemble, losing X material in the proccess (like how battery works, but at assembler);
Anyway, those are my ideas, I really think that this would give players another challenge to bypass, and a reason to use other sources of power.
*spiders live on an alien planet, so maybe they are immune to radiation?