BIG BAD WOLF: Ok, the stronger players should be protected to be bothered by challenges of the weakest, I agree. But it would be very normally to allow a challenge in a certain range. That range could be normally +1, 0, -1, but at the top down to -2 and at the bottom up to +2. That's the way a ladder normally works. I cannot see, what should be better with that stairs.
Btw, I would also prefer to allow empty steps with the interpretation to challenge to the next not empty step.