A small asteroid as a Cycler?
Here is a dangerous proposition, but an interesting one.
What about using a small asteroid as a Cycler ship? I say it is dangerous because you would have a large chunk of mass speeding around the Earth and Mars. You would want some serious safeguards so it never collides with Earth, Mars bases or Moon bases.
The advantage would be that you do have a larger chunk of mass in which to dock with and build on or in.