PearsonArtPhoto answers why it isn't done - generally NASA's very conservative approach to spacecraft safety, and hurdles it would set to get it implemented.
But assuming a miraculous change in NASA management and organizational culture, it would be fairly simple.
The engines have enough thrust to provide 4g of acceleration and are angled outwards and located around the outer edge of the capsule:
So firing a single pair, seriously throttled, on the opposite side from the parachute would provide enough torque (against the parachute line) to right the capsule, then all the engines could fire maintaining different amount of thrust, to keep it level before splashdown. Another alternative is to just cut the parachute rope, use Draco maneuvering thrusters to stabilize the capsule and perform a regular powered landing on superdracos.
Unfortunately NASA is the one with the money, so they make the rules, and Crew Dragon likely won't see the option of powered landing in any foreseeable future.