We should fix that.
Han Solo gets to be a woman. C3PO and R2D2 (yes, someone did play R2) will have undefined gender and can thus be played by anyone. Luke, Obi Wan, Vader, and Tarkin all remain male. Leia remains female.
The Empire is made of space Nazis, they can stay white
While not genocidal (the Death Star is akin to dropping a nuke; they've made no efforts to exterminate anyone) the Empire uses Nazi motifs too much for me to be comfortable casting, you know, people the Nazis tried to exterminate as Imperials. Hence them staying white.
But Firedrake is definitely right about women. Women can be Nazis. Women were Nazis; women are neo-Nazis. Star Wars is in a very different setting, there's no reason to assume sexism and there's already enough evil without it. The Empire can be non-sexist evil. Thus the Imperials should include as many women as men.
The Rebellion, the people in Mos Eisley, and so forth, are not made of space Nazis. The human extras in these places are split 50-50 male appearing female appearing (though androgynous people would be nice too) and the aliens where equivalent gender is apparent have the same split. In these places (looking at rebels in canon) there would be a sizable representation of aliens. (The Rebellion is supposed to be inclusive, so it should visibly include different people.)
Ok, that's casting.
Epic movies now are allowed to have epic length. Star Wars ran at almost exactly two hours. The Fellowship of the Ring ran 57 minutes longer than Star Wars.
Added length allows for added depth. More Owen and Beru, for example. Also, rather than leaving their charred remains laying out in the light, bury them or cremate them (properly.)
The Death Star weakness makes no sense BUT if there were rebel infiltrators on the Death Star then it could make sense. They've taken this exhaust port, quietly removed all of the safety measures, made a few modifications, and managed to get a straight line to the core. Presumably they do it slowly and without raising suspicions. Presumably it involved areas where you'd be checked for, you know, explosives, so they couldn't detonate it themselves.
It could even make the trench scene make sense. If the saboteurs were only able to disable the defenses in a single area (approach vector for getting into the trench) then you'd need to stay low or be targeted by everything and definitely killed. Why was it so distant from the target? Even with the other safety features on the vent shafts (the ones the saboteurs disabled on the special one) the Empire still knew better than to leave the damn things unguarded and so the saboteurs had to settle for an approach vector at a distance.
Also, the "initiating firing sequence" thing. It doesn't make sense either. They know how long it takes to get in position, they should charge on the way so it's ready when they get there.
If, on the other hand, the firing was delayed because they had to repair sabotage, that makes some sense.
I'd have an explanation for why it came out of hyperspace on the wrong side of the planet and thus needed to circle. For example: the jump of something that large is particularly taxing and leaves all defenses powered down so coming in close to potential planetary defenses or within range of fast but heavy hitting ships would be a bad idea, thus the trip around the planet.
This could be stated during the mission briefing on the Death Star.
Leia never mourns Alderaan. What the fuck? I don't pretend to know how people mourn in a galaxy far, far away (and certainly not how they did it a long time ago in said galaxy) but have her light some candles, say a prayer... something.
Blowing Alderaan up seems bullshit and stupid even by Imperial standards. If it were pointed out that it was known to harbor rebels and hide behind its no weapons policy when called on it, then it would be an effective demonstration. It would show that the post-Senate Empire wouldn't let bullshit stop it from holding rebel harborers accountable, even popular, traditionally immune from punishment planets were at risk, and the disproportionate nature of blowing up a fucking planet for allowing rebels safe haven (while not directly opposing the Empire) would encourage other planets to crack down hard on rebels for fear that if they didn't get rid of the rebels on their planet they'd be blown up too.
And Tarkin could say all of this in a menacing evil monologue, which would really make you understand how much of a game changer the Death Star is.
Honestly, rebellion on the Death Star could probably be a movie in itself, and the added time would only allow for so much of that, but it would be nice to see some of it because I refuse to believe that a population that large has no one who opposes mass murder.
Presumably most of them thought the station would be a deterrent, not actually used, and definitely not on a planet like Alderaan.
Which is to say, rebel agents should be only part of the people fighting against the loyalists on the Death Star.
I don't remember, did they say that they were giving Luke a ship because they needed them all in the sky and were short on pilots? Because they should. They should also have an explanation for why (e.g. a barracks at their last base was destroyed, really anything that would kill pilots while leaving the ships intact.)
Also, in some of the scenes that were cut, a friend from back home is featured (Biggs.) He turns out to be a rebel pilot and the two are reunited when Luke comes to Yavin 4 He could vouch for Luke's piloting skill to help get him in a ship.
And that, sort of, concludes it. Star Wars is a simple story simply told so it doesn't need any huge changes.
And, for those paying attention, yes, I did say that I'd try to have a Kim Possible decon post yesterday which is still not here today. Sorry.