Mike,
Regarding your last thought on the 20" rule. That is much simpler than current, which stipulates club length(s). 20" is 20", period.
Using the length of a club creates all sorts of inequities and inequalities. Do you choose a club length to maximize or minimize. If you have a club in your hand for convenience rather than by choice, what happens when a drop and roll is really close.
Should Yao Ming or Tom Thumb be advantaged or disadvantaged.
I have just glanced, and not thought or overthought the changes (so I may be incorrect here), but relief +20" plus 20" roll keeps you within a normal driver length of the relief point, which is much closer than the nearly 4 club lengths currently allowed.
But, you are right that a more simple solution is at hand, eliminating dropping completely and go to placing the ball; however I am willng to bet that one ruling agency thinks that is a bridge too far.