I'd like to see one.
Obi-wan Kenobi has to leave Tatooine for One Last Job™.
You can go a bunch of different ways with that and I think it could be fun, plus I'd like to see Ewan McGregor return to the role. He did a good job with a bad hand and it'd be nice to see him in a better movie than the prequels.
Heck, there was rumor floating around that we'd see a Star Wars meets 7 Samurai mashup in the early days of the new movie announcements. Have Obi-wan fall in with a group of Jedi in hiding who reluctantly decided to help out a small space/station colony fend off pirates in the Outer Rim. Some live, some die, and the day is saved. Obi-wan mentors a young force sensitive and gains a measure of redemption for his failures to save Anikin but things are left ambiguous at the end of the movie about whether any of the survivors managed to evade the Jedi purges.
Or maybe Obi-wan matches wits against an Imperial Inquisitor who is trying to capture a lost Jedi Holocron.
I could see a lot of fun to be had in a stand alone Obi-wan movie. Of course it could be terrible too, but that's a risk with any movie.
I say bring em on.
No you see he left the planet to go on an adventure that no one else knew about and he never spoke of again after the fact.
Is this really so hard to imagine? 18 years is a long time and the Star Wars Galaxy is a huge place. You really don't think there's any room for an adventure in there?