As a companion to [, what do you think about adding, for example, [ to mean delete line above current line if it is empty? I expect to use it often when correcting the number of blank lines before a class or def statement.
Seems kind of specific. What's wrong with kdd?
Also, I would suggest that if you're regularly getting yourself into an extra blank lines situation, maybe something is off in your workflow? Delete the blank line when you're deleting everything else.