Designing stuff is really expensive, using things made for Earth with minimal modifications really makes a lot of sense.
The steel is cheap on mars too (initially), since you ship it there anyways as part of the cargo starships, which aren't return to earth (since the energy to make fuel is initially really expensive on mars). Manufacture it in Mars and your basically just talking about shipping the batteries, motors, and a small amount of electronics (and machinery you will need anyways).
Don't get me wrong, I hope that little to no consideration was given to mars in the design. But if we happen to get to mars on Elon's most aggressive time tables (2025 iirc) it would make sense to base the vehicles on mars after this rather than designing from scratch. And it would make sense to keep the modifications reasonably minimal if possible.
No, it really wouldn’t. The base requirements differ so greatly that starting from scratch would be both cheaper and more practical. They are not different takes on the same vehicle, they are two fundamentally different automotives with extremely different terrain, durability, maintainability, and optimization goals. From the very start it is virtually impossible to go from a unibody design like this cyber truck to a true all-terrain body-on-frame construction and everything else depends on that.
And trying to design an optimal vehicle for mars is how you bloat the costs of your rover program by many many millions of dollars. Downmass is expensive, engineering is more expensive. The result of that is to take advantage of the fact that "mass cures a lot of sins" (Paul Wooster, SpaceX Principal Mars Development Engineer at Mars Society Convention 2019).
> true all-terrain body-on-frame construction
Why would you prefer this? It's just a form of construction that requires more materials, and results in a weak body that can be damaged. Furthermore, we get all the materials for the unibody design (lots of stainless steel) free from starships that won't return, and the material is easy to work with.
Mar's terrain is pretty simple. Rocks, and sand. We almost certainly will choose not to land on sand, so we only really need to deal with rocks. Cybertruck, really any earth vehicle with a reasonable clearance, should be able to deal with that well enough, maybe with some custom tires.
Thermal management, and problems relating to pressurization, are the only things that jump out as me as real difficulties. Neither sounds like it needs fundamental reworks though.
The steel is cheap on mars too (initially), since you ship it there anyways as part of the cargo starships, which aren't return to earth (since the energy to make fuel is initially really expensive on mars). Manufacture it in Mars and your basically just talking about shipping the batteries, motors, and a small amount of electronics (and machinery you will need anyways).