Books and comics have already explored this territory.

If there's one thing that experience can demonstrate, it's that there's a high probability that the stand-alone Obi-Wan Kenobi movie currently in development will feature the Jedi Knight taking on Tusken Raiders.
While it's currently unclear just when the Kenobi movie will be set, there are only three options that make a lot of narrative sense: the period before Kenobi's first (chronological) onscreen appearance in 1999's Star Wars: Episode I The Phantom Menace; the Clone Wars era; and the roughly two decades of time between events in Episode III Revenge of the Sith and the original Star Wars movie. Of those, the middle option is potentially problematic, given how much of that time period has already been covered in the animated series of the same name, and the first option perhaps packs little promise given that it is, technically, a time of relative calm before things started going awry for the Jedi Order. (Plus, the original Star Wars and prequel trilogies have already covered the "origin of a Jedi" arc such a movie would presumably be covering.)
Therefore, it's highly probable that any Kenobi movie would take place in the period where the character is in hiding on Tatooine, while the Empire rises throughout the galaxy around him. But of course it is this isn't just the lengthiest gap in Kenobi's onscreen life, it's also the most rich territory to explore and, tellingly, the same time period as the other Star Wars Story stand-alone features known to the world, with Rogue One ending just prior to the opening of 1977's Star Wars and the untitled Han Solo movie happening just a handful of years earlier, based upon the characters' ages. This 30-year gap of Star Wars history between the first two movie trilogies is, apparently, preferred real estate for Lucasfilm to build on.
On the face of it, this time period would present some problems for filmmakers. After all, according to earlier movies, Kenobi's disappearance during this time is so total that the name "Obi-Wan Kenobi" becomes a myth, with his disguise of "Old Ben Kenobi" transforming him into a recluse that's seen as, if not helpless, then certainly not as powerful as he actually is. How do you build a story around that? Thankfully, it's already been done in prose and comic book form, at least. (Not to mention, fan trailer.)
A recurring feature of Marvel's current Star Wars comic book is "The Journals of Old Ben Kenobi," a framing sequence in which Kenobi writes of his adventures during his self-imposed exile. These stories are intentionally smaller in scope than those traditionally shared in Star Wars, and see him working mostly undercover to deal with more local threats to local communities, whether they're bounty hunters, criminals or Tusken Raiders. Notably, these stories all emphasize that Kenobi is purposefully watching over the young Luke Skywalker and saving him from danger a connection already shown in the animated Star Wars: Rebels series, and one such that it feels unlikely any potential movie would be able to resist.
The same basic setup is true of the 2006 short story "The Last One Standing," which sees Kenobi protect Skywalker, Uncle Owen and Aunt Beru from Tusken Raiders, and also sans Skywalker of the 2013 novel Kenobi, in which the Jedi Knight helps settlers stand up to Tusken Raiders while trying to keep his true powers a secret. While both "The Last One Standing" and Kenobi are no longer canon, the Marvel comic books are, offering up an idea of what Obi Wan's life was like in hiding and a blueprint for any potential movie taking place during the same timeframe.
Should this indeed be what to expect in a future Kenobi movie, fans can rest assured that another part of the original film is likely to receive an unexpected prologue. After a Ponda Baba cameo in Rogue One, the Kenobi movie might finally give us the background to the character's first appearance in the original pic, shown below.