Honestly, I don’t really think you would have to establish too much in the crawl.
I definitely wouldn’t try to elaborate on Anakin’s history in the crawl. It wouldn’t fit and it isn’t really necessary. Obi-Wan reiterates in the movie dialogue that he’s trained Anakin since he was a boy (maybe cut “small” from “small boy”, and it could be interpreted as him being a teenager). A lot of the relationships are reestablished in this movie, like both Anakin and Palpatine reminding the audience that they have had a friendship for a long time. And we also learn through the dialogue that Anakin’s relationship with Padmé is a secret and against the Jedi code, which I still think is important for the movie to work and remain faithful to the themes of the saga.
All you would need to do is slightly alter the crawl to set up what the Clone Wars are and that the Jedi are fighting for the Republic. I would try to make that very concise and fit that in the just first paragraph.
Then the rest of crawl plays out the same, setting up the antagonists and the immediate situation with the kidnapping of the leader of the Republic. I’d also probably slightly alter the reference to Dooku to refer to him as a fallen Jedi.
Really take the crawl of A New Hope as a good example, it briefly introduces us to a war that we’re just being dropped into, just like we would be if Revenge was a stand-alone film. Ironically, Revenge “is a period of civil war” just like ANH!
I also think that you would want to trim any references that wouldn’t make a lot of sense without the context of the last two films, like anything about Anakin’s mother, unless you establish what happened to her in a dream or something (but I think it would still work without it, don’t make anything more complicated than it has to be), maybe the mention of the necklace Anakin made for Padmé, and definitely the final reference to Qui-Gon.
Maybe Yoda could just say:
“In your solitude on Tatooine, training I have for you.”
And then cut to Obi-Wan with an inquisitive look, then cut to the next scene.
I think that would be enough to help set up that there is more for them to learn, but keeps it mysterious.
Really the only issue I can think of might be that you don’t get the context of how Owen and Beru are Luke’s family, since they decide to take Luke there in the end. But without the previous two films, and with what Obi-Wan tells us in A New Hope, we can just assume it is Anakin’s family and what Obi-Wan tells Luke in ANH is generally true (minus his father wanting him to have his lightsaber and the stuff about Darth Vader, things Obi lies about to push Luke to become a Jedi).
A big change that might be considered is keeping Vader’s identity a twist, but I think what makes Revenge of the Sith work is the dramatic irony of knowing that this is the fall of Anakin Skywalker. At the very least, you could possibly remove any mention of Darth Vader from the film and cut any scenes of Anakin after Obi-Wan leaves Mustafar. But in a marathon context the audience would still know that Obi-Wan is lying, and later in ANH Vader refers to Obi-Wan as his old master. I just think you’d have to make radical changes and bend over backwards for such a change, and I think it would overcomplicate the movie and take away from its themes.
To maintain the twist, someone could just do the Machete Order, and put this standalone prequel film inbetween Empire and Jedi.
There are some other changes I think that would be worth considering. I know Dom’s ROTS edit intergrates OT music here and there in the film, and doing something similar with this project could help the movie fit in with the OT style more. Finding places to ocassionally reuse music and classic sound effects could help the movie feel more like classic Star Wars, since this film wouldn’t have the two other films to help establish the prequel aesthetic.
Dom’s thread: https://originaltrilogy.com/topic/Doms-Useless-Prequel-Edits/id/56746
Another edit I would recommend looking into for inspiration would be NFBism’s New Canon Cut. While his was meant to help recharacterize Anakin, Obi-Wan and their friendship to better fit with the Clone Wars tv show, I think a lot of his ideas, which include a lot of small changes, go a long way to help improve Anakin’s character in general, and I definitely would suggest anyone working on a ROTS edit to read through his thread and check out his edit: https://originaltrilogy.com/topic/Revenge-of-the-Sith-The-New-Canon-Cut/id/53990
I would also consider readding the deleted scenes of Padmé to help tie her story in with the Rebellion plot in the OT. You could even consider using Hal’s ending where Padmé survives if you wanted to try to be as consistent with the OT as possible. I would also encourage you to check out a recent post of mine from the Prequel Radical Redux thread where I suggest restructuring Padmé’s deleted scenes to help tie it even more directly to the Rebellion as we know it, and to better set up Anakin’s paranoia in the film.
Further down I also suggest an alternate way to handle her death to give her character more agency.
The good thing about most of these changes, if you don’t try to hide Vader=Anakin or to have Padmé survive, is that the movie can work as a Stand-alone film, but it doesn’t necessarily contradict the Episodes I and II either. Just because we cut out the references to Anakin’s mother and Qui-Gon Jinn doesn’t mean they don’t exist, but by removing those references, people who watch this edit can choose to either watch those movies, or just watch this plus the OT and it would work either way. By removing those details from ROTS, it allows people to interpret Anakin’s backstory however they choose, either as I and II present it, or as Obi-Wan describes it in ANH.
Sorry for the long post. While there are a lot of interesting 3-in-1 prequel edits, I do think with the right cuts, Revenge can still work rather well by itself. So this is a good idea for those who might want to do a marathon, but might not necessarily want to watch all three prequels.