Maybe I'm damaged goods, but I can't help but compare the new trilogy to setting up a new campaign.


Story:

When planning a 3 chapter campaign, I would defintely try to keep the same GM for all three chapters.

If I decided to have another GM for the middle chapter of a campaign I spent a considerable amount of time and resources on, I would make sure that it was someone good. (not someone who only GM'd one fairly big campaign and a couple smaller ones).

But if I did decide to let soneone else GM the middle chapter, I would at least try to cooperate with them on continuity between chapters.

And make sure that they at least had a passing familiarity with the campaign world, so they didn't implement scenes which retroactively invalidated stuff from canon or made it seem ridiculous.

I would definitely not go for a setup where the other GM only started writing his chapter after the group completed chapter 1.

I would also definetely tweak things in chapter 2 and 3 based on player feedback, but I would not start with a completely blank slate after finishing chapter 1. Sandboxing can be fun, but I like a little storytelling too to avoid too much randomness and contrived spur-of-the-moment ideas.



New NPC's:

If I made any NPC's who were Mary-Sue'ish, I would do it as a troll. I would try to come up with a phenomenal explanation for it, to be revealed to the players. And importantly do so *before* they lost patience with me and stopped playing.

Even so, I would probably only make them Mary-Sue'ish in one area, not a whole bunch. Lord Flashheart from Blackadder was the best rider, fencer, shot, and kisser in the whole kingdom. He was also deliberately made an annoying prat, because the writers knew the audience would empathize with that (Woof! Woof! to the magnificent, late Rik Mayall).



Old NPC's:

If we were playing in a campaign world that had beloved, established NPC's and institutions, I would not casually screw around with them. If I had to tell my Marvel players Captain America was dead, it would be the result of something major. I would not tell them that he had been shot while attempting to evade police after being revealed as a child molester, simply because I wanted my own NPC to take centre stage and needed him out of the way.

I would definitely not have old NPC's accomplishments casually overshadowed to prove how amazing *my* new characters are. It's infantile and just plain bad writing.
(To be fair, the Star Wars EU had a problem with this long before Disney took over.)



Flavor text/Cinematography.
I wish I could do it as well as Disney. Nothing more to add.



Sociological twists and political messages
If I wanted to insert subtle lessons into my campaign, I would not do it with a sledgehammer. In fact I would not choose any lesson which I knew was controversial and divided my player group.
I suspect that if I made all knights in trademarkblack armor be evil, that would be fine. If I made all knights having black skin be evil, I suspect I would have to start looking for new players.



Humor:
I see that Guardians of the Galaxy was a trendsetter, and everyone and their little dog too is copying them.
I'm more of a John Landis kind of guy. Humor used to break the tension can be amazing. Firing off jokes every 10 seconds is silly by design and just gets annoying after a while.


That's all I can think of right now.