Maybe one of the drops could be a ship mod or passive/activated ability (ability could come from a fully leveled ally; ally could be leveled by finding an Extremely Rare NPC boss or something like that) that improves your chances of finding Rare/Extremely Rare NPCs. Something like this:

L.U.C.K. Generator
The Latent Universal Combat Key Generator is used to scramble the cloaking algorithms of even the best hidden ships in the Galaxy.
Increases the chance to find a Rare or Extremely Rare NPC by X% for 4 hours.
20 Hour Cooldown.

(I don't know exactly how the game mechanics work, which is why I put X%, but something along these lines would be cool in my opinion.)

I'd like to see it at least a week. Would be cool to have a mission similar to the Christmas one, only the arti can be available every 12 hours instead of 20.

Any Holiday bonus mission and arti +1

+1 for that , id pay good GP for one of them