Terraform cycler asteroids

Speculation alert:  This alert was added along with the update below.

The idea popped into my mind. Here's what you might do that could be worthy of consideration.

You could use all of the materials that make up the asteroid in order to convert it into a suitable habitat that can sustain you while on a trip to and from Mars.

If a suitable asteroid can be found, of course.

It may well be preferable not to alter its trajectory, but just fly to it and from it.

It may also be preferable not to bring stuff back from it, just stuff that you need for your trip.  The materials found on the asteroid will stay on the asteroid.  Everything brought to and it would have to be taken from it after each trip.  That way, mass isn't added or subtracted.

If there are enough suitable building materials, you could fashion the thing into a large space station.  It would be spun up in order to provide artificial gravity.  The mass could be used for shielding for long duration stays in space.  You could also grow your own food.

If not everything can be provided by the asteroidal resources, then some stuff would have to be imported in. But that amount could be minimized.

It may also be preferable to use nuclear energy instead of solar.  That's because nuclear energy is so much more powerful and could aid in recycling all materials.  This would be done by heating it into plasma, which would cool down into its constituent elements.  Those elements could be recombined chemically into whatever materials needed.

Update:

Here's a drawing of the dumbbell shape of the proposed space station.  It would be spun up so that it could provide artificial gravity and would be terraformed inside the spheres at each end so that it could provide shielding, oxygen, and water.

Dumb bell shaped space station made of asteroidal materials and used as a cycler between Mars and Earth

Update:

Summarization of the goals for a terraformed cycler asteroid:

1. artificial gravity
2. life support, ie oxygen, water, radiation shielding
3. transportation to and from Mars
4. closed carbon and water cycles
5. simplicity of design
6. durable, made to last a long time 

Update:

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