i've been experimenting with using Monster Roles as templates to adjust the basic MM monsters - So on top of the standard monster you can make stat, HP, AC and attack adjustments for Lurker, Skirmisher, Defender and Leader/Controller versions.
Then these things like having a single Ghost entry (incorporeal, sunlight sensitive) with a selectable menu of abilities like: Grapple, Life Drain, Possession, Wail, Harrow, Insanity, Animate etc and then Wraith or Spectre or Poltergeist get relegated to single lines to describe any differences between them