I love the idea but in your own words,

It’s Ben Kenobi in the earlier episodes that is truly virtuous, noble and pure of heart. He’s our true hero. He’s incorruptible.

If that is the case, how does the hermit have a child? The rumor of Rey being the daughter of Luke and Mara Jade (never in the movies) brings another idea that carries some credibility in the idea posited on Reddit or somewhere else. First, Ben Solo, discovering Luke wasn’t as virtuous as he is supposed to be (i.e., he had a child) was what caused Ben to go haywire and strive to be his grandfather. Second, it provides a strong, force sensitive person. A Luke/Mara union would combine some powerful Force talent, which makes Rey as powerful as she is, where KyloRen only had one parent, the weaker of the two twins, who had the Force.

I’m regurgitating someone else’s idea but its the one that sits most comfortably with me today. I like your idea but where/when Ben Kenobi got jiggy is the only part to your story in which I can’t find a balance. Otherwise these are really good points and make this a much more rounded trilogy and conclusion to the nine!