Well, the ball could in theory feel how much pressure you excert on it and where, and provide haptic feedback. In a super advanced scenarion perhaps the ball could provide feedback by varying it's firmness. Guess it depends on how advanced technology is how good the thimble solution could be, but it strikes me easier to manipulate a ball, which you could do even when it's in a suit pocket than to do gestures in the air. Some gestures might be doable though. I have a hard time coming up with a "Cursor" scenario for that solution though and tactility makes it so much more easy to control. Maybe if you used your fingers against a hard surface but that would limit it's flexibility.
