Matt, I don't think 18 would work as a par four, unless they moved the green to higher ground. The blind shot into the green, even if they moved the tees up would be pretty extreme.
Jerry, there is some truth about wanting it to be a par 5. However, as I understand it, the original plans had the tee box on the 17th hole side of the little stream. That would have made the hole very different from the one we have now. It could have been a much more exciting tee shot than the one we have now. The DNR did not let that happen, hence the long walk to the tee and a tee shot that inspires little fear or thought.