Over the years, I have used all manner of weight belts (standard, with pockets, non-ditch harness, a ditchable velcro style harness, seasoft neoprene belts, DUI classic, standard with pockets, several kinds of buckles, etc.) and prefer, by far, the DUI classic.
Hypertech: I disagree. First, the DUI has two pockets (and one rip cord) on each side. That means one could, using your method, easily drop less than 20 pounds at a time. Second, one can configure their weighting in any number of ways (backplate, bold-on weights, trim weights, etc.) so that the belt is holding less than 40 pounds. That means you could easily configure the belt so that you could drop less.
All of that said, I also think some of your concerns are misplaced. First observation: treating the bends is easier than treating drowning. Second observation: IMHO, the best way to stabilize a diver thrashing at the surface (where many problems occur) is to make them positive (and, ideally, very positive). The easiest way is to dump weights. Third observation: assume you are negative and are not able to take appropriate action (injury, panic, etc.). This could be at the surface or at depth. It could be with the diver thrashing or the diver immobile.
What is easier: pulling a ripcord or pulling individual weights out of pockets or using a cutting tool?