I'm not sure how efficient the drone would be in slowing down the free fall. Not very efficient, as my guess. Since the balloon would carry the drone to a very high altitude, the drone would likely start rotating during the free fall and it would be very difficult for the propellers to get it in a stable position again.
Also, who would control the drone to do this? Would it be programmed to land automatically? The remote control connection would fail. To design a drone that can stabilize itself and get back to the lift-off location automatically might significantly increase its price.
I propose at least equipping the drone with a parachute that spreads automatically once the drone reaches a suitable altitude. Then it might reestablish the remote connection to be controlled manually (given the winds didn't carry the balloon with the drone too far away to the side) or get back to the original coordinates automatically.
Another option would be to simply attach a camera with an automatic parachute to the balloon. When the camera lands, it sends the signal with the coordinates to a dedicated app on the user's smartphone. The user then navigates to the place and picks the camera. In this case, the location from which the balloon is released has to be chosen wisely - uninhabited area, a field with no or few trees, no water bodies, etc.