I've written at great length about the many problems with the Star Wars prequels (including of course the Man of Destiny series), but one area I've neglected is the problem of creating tension within the story.
Yes, it's possible to keep an audience's interest in seeing how a character gets out of each scrape. This is the foundation of the James Bond franchise. No matter how bad things look, somehow Bond survives for yet another adventure.
I'm not particularly interested in those kinds of stories, however.
I think the best way to pull off a prequel is to relegate the known main characters into supporting roles.
This allows other people (who don't have script immunity) to come forward and provide the proper dramatic tension. It can be interesting to see how events formed a future hero, but for those who want actual suspense, you can have that with all the additional characters getting bumped off (or looking like they might get bumped off).
I will say that if you are going to make the future main characters take center stage, the demands for a very good story become that much greater. And as noted above, that's hard to do when physical danger is categorically out of bounds.
In fact, emotional danger's also largely taken away because they have to come out reasonably intact. I'm tempted to say that prequels are by nature locked into a static characters, but that's not entirely true. You can take a beloved character and show him as a complete dope who will turn into something more familiar.
But even there, with the outcome known, it's critical to make that path of that progression really interesting.
I've been asked a couple of times to write a prequel to Man of Destiny and the natural thing to cover would be the Deimos War. It's vague enough that I'm not giving anything away and any "crossover" characters from Man of Destiny would be children.
The thing that holds me back is not just the potential scope of the project, but the fear of giving in to "fan service" type call-backs. If I were to do it, I think I'd have to write it as a standalone book, explaining everything anew. I think only then would it be worthwhile.