I want something like this.
Power will power your shot but won't effect height that much (unless you power it high enough), but it would be rather direction effected. For example you press down and left +power it up to where you're suppose to to make a powerful low shot and press up and left + power it up until it's enough to make a high powerful shot.
Ofcourse, the powerbar will still effect the ball's height but not as much since you'll control it with directions.