Putting forward and back spin is an option by adjusting the dot up or down on the golf ball before hitting your shot. Of course, our current clubs (starter set) don't give much spin when used but it is still there. Newer clubs, when they come out, will give more spin.
I think everyone agrees, the distance for the putter should be able to be changed but if you read past threads, you'd find that this has been talked about more than President Clinton's hummer. This problem is on the WGT "fix" list as WGT has stated in some of those threads.
Why would anyone want to hit a club less than 50% other than when putting? Also, why would you increase the scale above 100%? I guess it could work, as some people are able to hit farther on demand, but you would loose accuracy as the "sweet spot" would get considerably smaller.