Not sure if you're arguing with me but, It could have been the most interesting thing. But it wasn't.
I'd make a Vader movie that takes places between 4 and 5, put him in the Emperor's doghouse after the death star goes down.
In one of the reports leading up to R1 I think Kathleen Kennedy said the standalones would be about non-Skywalker bloodline stories in the SW universe. So ... no Vader, because he is a Skywalker.
OK, so I watched R1 for the second time this weekend. I picked up a few notes I kind of missed...
It's been >3 weeks, so we can stop using spoiler tags right? Anwyay - SPOILER WARNING-
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The first time I watched I totally missed the argument for why to go to Eadu. Or, it went in one ear and out the other. Jyn needed to provide confirmation of the information from Galen to the alliance because nobody had seen the hologram except her and Saw, and I think I had been distracted by other stuff the first time I watched.
One thing that still doesn't make sense is why Saw was just like "cool, you guys get off planet and I'll just hang back and die". For no reason. C'mon, make him war weary, or give him some noble suicide mission, or have that outpost on Jeddha be his childhood home he refuses to leave like a cantankerous old curmudgeon townie when the big hurricane is bearing down. Or at least give him a ship to jump onto that gets hit by a giant boulder or something.
The other thing that I didn't connect was that Tarkin is explicitly told that Krennic is at the base in Scarif, and then later destroys the base, in the process killing his rival. This could have been played up a little in the script. Let Tarkin have information of what the rebels are trying to accomplish, which is tied to the shield going down so they can get the signal transmitted (by the way... the shield blocks data transmissions from a big, presumably high powered radio dish on top of a tower, but audio goes through the shield with no problem? There was some radio communication between the Alliance ships and troops on the ground... right?). Once the shield goes down, Tarkin has cover to act. Destroying an Imperial facility should have been presented as a last resort, but still logical course of action for Tarkin. Have his subordinates object "but there are thousands of our troops at the base! and Director Krennic is on the platform!" and then Tarkin has a bad-ass quip about the rebellion being stopped at all costs or something.
On second thought... at this point Tarkin does not know that the rebels are in possession of the plans, or does he? Maybe he suspects it. And I might have to watch a third time - he knows the rebels want the plans, but does either he or Krennic know that Galen baked in the vulnerability? All they know about is the pilot and Galen. Hmmm... In any case, we could have used a more dramatic moment for this decision. Maybe in between R1 and Ep IV Tarkin gets is ass chewed out for blowing up Scarif, the way the Captain in 80's cop movies chews out the renegade cop....
And on other note. I didn't think CGI Tarkin was quite right in 3D. When I watched again I went to a 2D show and hoped it wouldn't be as bad... but it was still kind of in the uncanny valley. His cheeks were cartoonishly hollowed out and it made me feel like I was seeing a character from SW Rebels with slightly higher resolution texturing. Well, maybe not quite that bad, but it didn't quite ring correct. Almost there. I did have a much bigger lump in my throat when CGI Carrie Fisher was onscreen after her passing.
Oh and Vader's castle... the interior was fine, but could they not have ripped off LOTR on the exterior? LOL...