Cham:
I again wish to thank you for all you have done for Celestia. Your models and add-ons are just stunning. My Astronomy students have praised them numerous times, and as you know, teenagers are very hard to impress!!
I second everyone's call for a Mars ship that contains a rotating section. It is absolutely vital for inclusion in a real transport to Mars, so it should be in your model.
I am unaware of the size that a ship from Earth to Mars would actually have to be, to carry a crew to Mars for an extended visit. The Kepler seems too big, the taxi seems too small ... the Carl Sagan seems about right ... what has your research discovered about the dimensions of a Mars transport?
I also support your desire to include a surface landing vessel in your Mars transport. Obviously, we have to get down to the surface, and back again. If you do include such a spacecraft, if would be IDEAL if it could actually be shown separately as well as a separate add-on, so us storytellers could tell a story about it leaving the transport and heading toward Mars.
You may ... or may not ... have ever seen a Hollywood movie called the "Mission to Mars". It is a far-fetched science fiction tale about an advanced civilization leaving a huge artifact on Mars for humans to find. However, the ship used in the movie to get to Mars is a good model that might interest you. The movie also has some great scenes of Newton's laws at work in space.
Anyway, keep us posted on your efforts to mesh everything together into a Mars exploration add-on.
Frank