There is only one reason I can see for someone drowning from starting a descent with the air turned off. It seems they must be too heavy. If not, they could just return to the surface with a few fin kicks. There's a big difference between recreational diving and tech diving, in equipment, skills and corrective actions. A recreational diver in a wetsuit should be light enough that they should have to duck head down and kick to descend from the surface. If they can just dump air and get down, they are too heavy. In that case, if the air is off, getting back up is easy; just stop swimming down! That way, there is no issue of having too many choices to take, or choosing the wrong path to remedy the problem. If you do nothing, you will likely float back to the surface if you haven't gotten too deep already, and simply doing what feels natural IS the right solution (swimming back up!).
Personally, I think the industry has made a big mistake by making the BC standard and "required" equipment. I think most divers would be better divers and have safer more enjoyable dives if they didn't use BCs. I think a BC is a piece of specialty equipment and it should be treated as such, with special training to teach people how to use it properly for those dives that it should be used on, and also the gradations of use from cold water recreational use to full tech use. If people didn't normally use BCs, they wouldn't normally dive overweighted. Nearly everyone's attitude for proper weighting would be shifted toward a better position.
I have accepted taking a lot of flak for my "BC's are inappropriate for most recreational diving" stance. But, this is how I feel. Whenever I hear about these deaths, it just seems senseless and very sad.
I also like the idea of making BCs too small to allow for someone to dive overweight. If the standard recreational BC were to only have about 8 to 10 pounds of lift capacity, it would be darn near impossible for someone to dive with too much weight to prevent a swimming return to the surface, while still retaining enough buoyancy authority to offset suit compression and air consumption. If they were too heavy to swim back up, they also wouldn't be able to float on the surface with a fully inflated BC. The overweight situation would be glaringly obvious long before attempting to dump air and descend. With that, there could also be the added benefit of really small, streamlined and cool looking gear, instead of the baggy and ugly looking equipment usually sold in the LDS.