Here is your modification! Another outpost is glad to take those parts.
Interstellar flight conversion. Cost -15 RU (refund). Mass -5 units. Size -5 (refund). While all outpost ships are designed to survive the long flight, they also have more traditional reentry systems, rockets, high tensile strength parachutes, crumple zones and other devices to slow down and crash with some level of grace. By not installing these you can save a small amount of mass, and resources and use the extra space for something else. Some other means for traveling to the surface will need to be devised, as the former 'falling brick' will now become an 'Egg shot out of a cannon'. Nothing but burning scrap will survive an encounter with a planetary body.
Here is the start of an atmosphere creator, making a scrubber and taking a hydroponic system would be possible as well. You could research a generic central system to supply your areas. Bringing some extra air would give you a measure of time to build an adapted device as well.
Oxygen Extractor. Cost 5 RU. Size 2, Mass 4. Oxygen is a must for human life, but it is not always conveniently available in a breathable format. Recycling units can also break down, and do not offer a solution to expand a population. This all-purpose unit can process any atmosphere containing even trace amounts of the precious gas, and separate it from the other - probably lethal – compounds present. Requires 10 MW of power, produces up to 5 000 liters of pure oxygen a day, provided high enough concentrations in input material.