In my opinion, it would also be good for filling in plot points unaddressed by the prequels, but which I greatly care about. Before the prequels came out, I assumed that Obi-Wan Kenobi's arc would be just as important as Annakin Skywalker's; I sort of figured that the three films would play out as a the story of their tangled relationship. Instead, Skywalker is a little tot when they meet, and their relationship seems rather shallow. Their lightsaber duel on the lava planet was epic, and Obi-Wan's bitter words for the burned up, defeated Skywalker provided maybe the one moment of true goosebumps in all of the prequels. However, I had thought that this would come at the end of the second movie, and the third would be an adventure where Obi-Wan had to figure out how to protect the Skywalker twins while living with the horrible guilt of seeing his Jedi friends hunted down and murdered by the very man he had trained. Instead that whole story is tossed off in about five minutes at the end of the third prequel. I'd really love to see a Star Wars film about Obi-Wan's struggle to survive the Jedi massacres and come to grips with his own responsibility via his failure to keep Anakin on the right path.
From the earliest days I watched Star Wars flicks, I thought Kenobi was an extremely compelling and complex character. In many respects he was a broken man, a once great person reduced to being a hermit on an isolated planet. He obviously carried around a great deal of personal guilt, evident when he admits to Luke that he thought he could train his father as well as Yoda, and was wrong. (He is still feeling this guilt in the afterlife!) After all, his failure contributed to the destruction of the Jedi and the Old Republic. He then had to spend years, alone, thinking about this. I can't imagine what that does to a man's soul.
In the end, however, he redeems himself. He manages to introduce Luke to the Force before sacrificing himself to save Luke's life. He guides Luke to Yoda, and gives him the strength to confront the man he now knows is his own father. For some reason, George Lucas became obsessed with making the Star Wars films into the redemption story of Darth Vader, when it is Obi-Wan who has a much more interesting path to redemption. He is not some kind of prodigy or chosen one, he is a person who made bad decisions out of good intentions, and has to live with the pain and suffering those decisions have caused. That's something a lot of us can relate to.
Perhaps it is this experience that makes him a bit of a moral relativist, especially for a supposedly pure Jedi. For example, he tells Luke that Vader killed his father, and when Luke comes back to Dagobah to confront him, Kenobi tells him that what he had said before was true, "from a certain point of view." He goes further, and explains that "many of the truths that we cling to depend upon our point of view." Kenobi also chides Anakin during their duel, rebuking him by saying "only Sith deal in absolutes." He has a remarkably postmodern perspective, considering the binary good vs. evil story told in the Star Wars films. That perspective makes Kenobi much more relatable to us than any of the other Jedi.
What kinds of films about Obi-Wan from the time of Darth Vader's creation until his first meeting with Luke could be made? How about My Dinner With Yoda, which follows a two-hour philosophical conversation between Kenobi and Yoda in the latter's Dagobah hovel? Like the characters in My Dinner With Andre, they are on hard times, and are trying to figure out what life is all about. Or perhaps the film could be Old Ben, a character study where Kenobi is known as the eccentric old man of Anchorhead while hiding his secret past that he must confront. I know this all sounds silly, but if Disney is going to produce a film in the Star Wars universe every year, why not go for broke? Why not make something arty? At the very least, why not feature the character whose damaged soul most resembles our own?