I'd just give each enemy a private variable that decides if you've grabbed it or not. When your projectile ring thing collides with the enemy, set the value to 1. When that value is 1, deactivate the enemy's behavior (or just create a new object and destroy the enemy) and position it to the top of your player. You can then have another value to tell the player if he's holding something or not, and change his animations.
To throw an enemy or object just give it the ball behavior with gravity and, upon throwing, set it's x,y velocities.
Sorry maybe not the best explanation but there isn't much to it!