I am aware of the downshifting, and I do this when I drive other cars or in the hybrid down very sharp grades where the generator doesn't cut it. However, I've heard conflicting reports about downshifting, some say it's very prudent, others say that it's unnecessary wear and tear on the engine and drive train. An electric motor uses magnetism rather than friction to provide the resistance, which is was my main point. I agree about the battery being much more expensive than brakes, but the brake-saving is just a side effect of them, anyway. (the ~10mpg savings is the main effect)

Your ellaborate cruise control options are a good suggestion as well, especially being able to specify a range (ie as slow as 60 uphill, fast as 75 downhill)