I think a programming intensive off season project sounds amazing. The
Guitar Hero project is an example of something that isn't a full robot, is a good stretch, and will definitely impress crowds.
My point is that the project you describe is comparable to RoboCup, which is graduate level research. Attempting to do the whole thing in an offseason is a bit naive, but if you break it down and focus on one aspect that you are most interested in, learn a lot about one type of sensor, or one type of control, or learn about Kalman filters or path planning, this becomes something that will have impact on your team and on your abilities.
If you don't think something like that is ambitious enough, coordinate it with a few others, but again, plan it out, layer it so that you can make progress one step at a time.
Greg McKaskle