Played this game enough so that I thought I'd know what the ruling would be, but I'm not 100% sure.

First turn, DS deploys a Human Replica Droid as its only unit. LS brings out Luke Skywalker to slice and dice the Droid, and he succeeds. DS Intimidates Luke, though, so he's still got a focus token when DS's 2nd turn starts. DS opens up with Force Lightning to destroy Luke. LS tries to play Lightsaber Deflection... and I wasn't sure what should happen. There's no DS unit to apply damage to, so does the Lightning just get deflected off into the ether? Does Luke take any damage? Can the Lightning be deflected in the first place? Am I thinking too hard?

No. Lightsaber Deflection doesn't work on Force Lightning .

Force Lightning doesn't damage a unit, it outright destroys it. Since there is no damage to deflect, the event is an invalid target of Lightsaber Deflection's interrupt ( When damage is dealt to a friendly non- Vehicle unit ) [...], and thus you can't play the Deflection.

Just think of it as Lightning skipping the "deal damage" part and jumping straight ahead to the "destroy" part of getting rid of a unit.

Also, the only way I can think of to get Intimidated on Luke that first turn is if the DS has Jabba on table. In general, you cannot play Enhancements on your opponent's turn.

As a side note, if the DS had played Force Choke (to try to damage Luke) while Luke was the only unit on the table, the LS player cannot use Lightsaber Deflection as they will be unable to target another unit to deal the damage to.

No. Lightsaber Deflection doesn't work on Force Lightning .

Force Lightning doesn't damage a unit, it outright destroys it. Since there is no damage to deflect, the event is an invalid target of Lightsaber Deflection's interrupt ( When damage is dealt to a friendly non- Vehicle unit ) [...], and thus you can't play the Deflection.

Just think of it as Lightning skipping the "deal damage" part and jumping straight ahead to the "destroy" part of getting rid of a unit.