Again, herein lies the problem.
They can mess it up as easily as they could nail it.
Just naming the character and already each of us has an idea in our minds about what the story should/ could be. Ben Kenobi. He's so iconic that just suggesting the idea of a movie or series based on him conjures up all kinds of ideas. Do that for any character. Darth Vader. Luke Skywalker.
It doesn't even matter how big or small a role they had either. Their is a fan base for even the most obscure characters.
We wouldn't have this issue if it was a totally new character. Which is why using events and people we already know proves how creatively limited the series really is if they have to constantly rely on everything that is already known.
Would it be cool to see Ewan portray an older Ben Kenobi? Sure! Though I seriously doubt that they will do the character justice with the script and it will likely pisses me off.
My advice is to just leave well enough alone. Venture out to another part of the galaxy and if Star Wars is truly as limitless as people claim it to be then it will stand on it's own when they try new things and reinvent it by going elsewhere.
All that being said, here's what I would like to see.
A small scale adventure/ personal journey. The tone would be more like a Western where Ben learns how to adapt to desert life after living his entire life on Corouscant. Living off what little is there in the wasteland. Fending off Tusken Raiders. Krayt Dragons. Bartering with locals. He gets reluctantly pulled into a conflict on Tatooinne, all the while trying his best to keep a close watch over Luke. We could also see him trying to live out the ideals of his Jedi teachings and forsaking his own desires to try and live simply. All the while coming to grips with his own failure with Anakin, dedicating himself to protect Luke and one day teach him the ways of the Force. We could even see him training to become one with the Force.
I've always said that if they were making anthology movies they should just pick a genre and make a movie using that tone. So for this movie the tone would be a Western.
For a Jabba the Hutt or Boba Fett movie the tone would be a Mobster movie.
For a Qui-Gon Jinn movie it would be a Samurai movie.
Use the genre and the tropes of those genres but just set them in a galaxy far, far away and they could do all kinds of cool things with it. Mimic shots to replicate certain scenes from those genres as a way to pay homage to not only the genre but to film itself and don't use modern movies to do it either because then it's too easily recognizable. Sadly I think they are just too short sighted to understand that this is what is missing from their movies. Too often these film makers don't even have much of a cinematic language enough to think like that.
Just rehashing shots from the original trilogy in a new Star Wars movie isn't an homage either because Star Wars is not a genre. Space Opera is a genre. That's why Lucas used Flash Gordon, Westerns, Robin Hood, and WWII movies and mashed them all together by mimicking shots from those kinds of movies to evoke a sense of familiarity.
Example:
In LOTR there is a shot where the Nazgul ride out on horseback from Minas Tirith to find the One Ring. The camera angle is low and the shot looks like it was taken from a Western the way it's framed. It's a cinematic homage to a genre but set in a fantasy world instead of the old west.