Wouldn't it be easier to add some rope pulling the capsule to compensate for the air resistance? Or would it add too much "noise" because of the imperfections of such system?
The longest vertical shaft you're likely to find is around 3km, which gives you a little over 20 seconds of freefall and a couple seconds of violent deceleration.
But the problem is, you're dealing with acceleration squared. The Bremen tower already does almost half that time (9.3s with the slingshot), so it's probably not a big enough difference to warrant the effort and travel.