That's pretty much a given. I mean what's the point of switching them if they each end up doing the same thing? I already have some ideas about how alt-ANH might go differently, but the inciting incident kinda needs to be the same; meaning Luke still needs to send R2 down to Kenobi with the plans, and Leia would still need to find part of the message that sets her off on her Hero's Journey. To my way of thinking the waves of change should start small then propagate outwards. Meaning ANH would largely play out the same in terms of the broad gestures, while tESB might be quite different, and RotJ might be all but unrecognisable. Keeping in mind of course that the Will of the Force is still going to be at work, whatever choices are made. Yeah, like I said it wouldn't be very interesting if you just recast Leia as a female version of Luke & visa-versa. These characters are who they are, no matter where they're brought up. There is some potential in something like that idea; which is more about extrapolating that brief time between the third & fourth drafts when Lucas considered making "Luke" a teenage girl (which still survives in certain pieces of concept art.) I don't recall what his ideas were regarding the "Leia" character in that incarnation; whether she's replaced by a male version, or simply removed altogether in favour of the McGuffin (though I'd say keeping them both girls is interesting, albeit a little too progressive for the time.) Honestly I think the flirtation with the concept was so brief, he may not have thought it though that far before just switching back. Either way, that's a whole different thought experiment.
About the same as Luke I'd imagine. She may not hit quite as close to home for him as Luke in terms of reminding him of Anakin, but I can't see anything being wildly different in his feelings of guilt and how he finally overcomes them. Except maybe he didn't give her a toy airspeed, but a holobook of galactic history, mythology, or an atlas or something. Something to spark an interest in the wider galaxy.
We would assume Luke would have some great resistance to the mind probe Vader gives him. The question would be if Vader detects the Force in Luke at this point, or if he ever started showing traits earlier. What if he did start showing a few years back? Would he have lessons to hide it from Alderaan, or would he have gotten training from Kanan or Ahsoka? Or would Luke be naturally difficult to probe, like Leia deflected Riva at the age of ten with no force training.
That's another thing that I think would go more or less the same. Vader never felt Leia's sensitivity, and he was in very close proximity to her for quite some time. No reason to think it would be different with Luke. If anything, as far as the interrogation goes Luke might be less resistant since it's obvious which twin is the more stubborn and has the stronger force of personality alone. Keep in mind that the mind probe is just a drug cocktail from the interrogation droid, not that thing where a force user can extract information. I know that's not often very well explained, but from context clues I don't think it's actually mind-reading per see, so much as passively sensing feelings (as Ahsoka did with Grogu, and Vader with Luke in the throne room) while also imposing an invasive compulsion. Like emotional sonar; send out a "ping" and listen for an echo. Though in this case the "ping" is a push upon someone's will, and the echo is any strong feelings that float to the surface. So it's more about intuiting than "reading". Remember that the force can have a strong influence in the weak minded, but being able to resist it just shows that a person is strong minded, not necessarily force sensitive. It's all about willpower. So of course Stormtroopers and low level Imperials are universally susceptible, while even three Jedi working together could not compel the likes of Cad Bane (though it did work indirectly as a form of torture, which incidentally is much more like how the Sith would do it.) That's probably where the mind probe is supposed to come in; wear down the subject's will so Vader can compel her to disclose the location of the rebel base. As for the intersection with Rebels; again while the details might be different, the mission to Lothal would have worked out about the same. Force abilities fade quickly in even those born with a strong connection, which is partly why Jedi prefer to train them young. By the time they're teenagers, both Luke & Leia had become fully formed people and had "learned" what's impossible, so while they would always have that connection; without instruction they wouldn't be able to use the force in any especially significant way. Luke got some of that instruction from Obi-Wan, so by the time he's flying in the Battle of Yavin, he's actively (but still rather minimally) using the force, which Vader then does indeed sense. In this version of events it's Leia that would have received that instruction (and her father's lightsaber) so it should be her that uses the force and blows up the Death Star, gaining Vader's attention. However there's a slight wrinkle there since in either "timeline" (for want of a better term) Luke is still the better pilot, so why would an OK bush pilot like Leia Skywalker be jumping into an X-Wing over a known hotshot like Luke Organa? I'm still playing with ideas, and I have a couple different notions of how Yavin might play out in this scenario. The easiest option is for simply for Luke to be Red Leader, and because they'll take anyone that can fly; Leia jumps into Red Five and they both fly the trench run, with Leia's shot finally being the one that hits the mark. Another is for Luke to be injured and unable to fly somehow, so Leia takes his spot while he watches from the control room. Not very interesting and a bit of a cop-out, but it would simplify things. One other scenario I've been mulling over has them both flying in a Y-Wing; Luke piloting, Leia as gunner/bombardier (yeah, I know the Massassi group Y-Wings are mostly one-seaters, but it's an easy thing to alter for the sake of the story.) So it's still Leia who shuts off the targeting computer and Luke has to hold steady and trust her with Vader still baring down on them both. I kind of like this idea since it feels like the right balance of familiar and new, while letting the characters stay true to themselves in these altered circumstances. We'll see.
I suspect the meaning of the term changed over time. Initially it was the kind of technological thing you'd expect to see in Flash Gordon, but ROTJ begins to paint a different picture, the endpoint of which is on display in the sequel trilogy.
I always liked the two seater Y-wing so this concept works better and honestly is a bit more interesting with Leia instead of the passive role she has in ANH. Do they call it "mind probe" or is that an assumption?
"Mind probe" is specifically said in ANH, and while I haven't double checked, I'm pretty sure in 'Rebels' Price specifically refers to the injection as such in Hera's interrogation.
In that case no, the only time mind probe is mentioned by name is in those two scenes (plus this deleted one) so far as I'm aware. I wasn't very clear either; the initial point I was making is that people seem to assume when Vader said "mind probe" he's talking about a force mental thing, where in fact it's whatever the interrogation droid is doing with her. Indeed that second deleted mention does line up with the idea that it's an ongoing process, likely with multiple sessions. This is one of those things where it pays to remember that Lucas was channelling 'Flash Gordon' a lot with this kind of stuff, so of course there's a "mind probe" machine to menace the captured Princess with. There really isn't name for what me see Kylo, Vader & Maul doing since there's really no such thing as specific "force powers" per see. It's just an application of several aspects of tapping into the force. Sensing emotion. Projecting one's will. Possibly a little foresight and guidance from the force itself to the correct conclusion. Indeed, one might conclude that Luke does the same thing for Grogu in a more gentle, sympathetic way when he helps him remember Order 66. The way a Jedi senses and constantly experiences the universe around them in a fundamentally connected way is one of those things what's often forgotten by the audience since it's not easily visualised. I suspect Lucas deliberately shied away from depicting straight-up telepathy since it would be too easy to overuse as an easy way out of predicaments. The closest he got was Luke calling out the Leia, and the exchange between Luke and Vader during the escape from Bespin, but even that is ambiguous as to whether they're literally talking to each other in words, or if that's just a trick of the edit and it's just a non-verbal exchange of feelings ( which lines up more with what Ahsoka says about Grogu and her communicating.) This is incidentally one of the things that annoyed me about the ST with Rey and Kylo having force zoom calls (that also somehow became force teleportation?!) You allow that kind of power creep to set in and it erodes any sense of peril. Lucas never wanted the force to just be "magic", it's meant to be spiritual; a way of perceiving and interacting with the universe itself.
This. Along with the story creep. Vader doesn't detect Force sensitivity in Leia in ANH because she wasn't Luke's sister or Force sensitive when it was written. The first time Vader directly encounters Luke (trench run) he immediately detects it, even from another fighter. Not sure I buy Luke as Red Leader, but maybe flying at Yavin to backfill the losses Red Squadron suffered at Scarif. If we go with the idea that Luke and Leia tend towards their original strengths, then maybe she's the one who convinces Han to go after Luke and shoot Vader off his tail at the end. Like maybe she's in the Falcon's gun turret when that happens... Reverend is coming up with some really good ideas, though!
On second thought, maybe I do buy Luke as Red Leader under the right set of circumstances. Say he does learn to fly as a youth on Alderaan, then meets Ahsoka Tano during his interaction with Spectre Cell during Rebels. She recognizes him as Force sensitive, and gives him the same rudimentary training that Obi-wan gave him in the original. Or Kanan Jarrus does. So his skill as a pilot is quite augmented, and rather than 'staying at home' on Alderaan like Leia, he gets 'out there' like Mon Mothma's niece in Andor, actively participating in the Rebellion as a pilot. Maybe he fights at Scarif as Red Leader, and takes the plans himself to Tatooine with Artoo in search of Kenobi. His X-wing is shot down and he is captured, but Artoo escapes with the plans. (Very similar to the beginning of TFA, when you think about it.) Or, he doesn't get captured, and Luke, Leia, and Obi-wan take the DS plans directly to Yavin. Then we're off into some wild terrirory and I'd have to give that one some thought.
So who negotiates the deal with Chewbacca and Han about going to Alderaan? Ben? Leia?...Luke if he has somehow evaded capture? If Luke is still imprisoned on the Death Star, how does Leia convince Han to break him out? Does Luke have the garbage chute plan, or does Leia still logic that out as a farmgirl?
Side problem. Leia is way too short to be a stormtrooper. Luke and Han managed to get away with it, but Leia's rather noticeably shorter than Han.
Luke would have gone to the academy to become a fighter pilot, skipped 12 rungs, and started on day one in the Imperial Navy as the Captain of a Star destroyer, which is more about requisitioning toilet paper than close formation flying. Luke is a droid diddling drunk