This would diminish college basketball on multiple fronts. Guys that are obviously good enough to get drafted go straight out of HS, and the ones that could stand to improve draft stock or develop their game for a year or two, a la Marcus Smart, end up at JC's playing for teams you've never heard of and will never watch. In essence, it filters a good portion of NBA talent from ever seeing D-1 ball.
What is so offensive about the 1 and done anyway? Any person in any profession that can make millions after a year of college and ANY sensible person says 'Good for him!' ... except sports. When it's a college basketball player, it's offensive for some reason. I don't get it.