In the new snapshots you have noticed the new boss, the Wither. The Wither requires you to kill some Wither Skeletons in order to summon it, and currently they only spawn in Nether fortresses. I think since that they look like burned skeletons (withered), when a skeleton is struck by lightning it should turn into one of these new skeletons, but without the stone sword and instead with a bow. Perhaps a 50/50 chance or so, since I know lightning strikes often during a thunderstorm. I don't think I would need pictures here since basically it is self explanatory.
That would also give a backstory for the Wither skeletons.
Free + Crabs + Ability to trample/suffocate opponents in Cortex Command = Free Bombs.
It wouldn't be much easier at all... Lightning striking a hitbox is really rare.