Having smaller Oxygen Generators will allow submarine designers to fit a number of them in a room, for instance.
Each one of them could be linked to vents in different decks or sections like engineering, command, medical, etc.
Wiring them with Relay Components and then a power grid, then wiring the relays with buttons to toggle them on and off will allow the crew to turn on and off the oxygen generation for these decks and/or sections at will.
Here's the sprite I use for these in my mod:
It's small enough to fit at least 3 of them in about the same space a Oxygen Generator uses.
OLD: Basically, the ability to turn on and off vents in rooms. It could work by wiring a Vent to a Button and/or having a HUD system in an Oxygen Generator so players with the right ID card can toggle them on and off.
This could be used as a different way to deal with fires or human intruders in rooms.
In the usually common case of running out of power, maybe an Oxygen Generator would turn randomly selected vents off one by one depending on the power input. Players could prevent this by shutting the vents off manually.