That is such a difficult question for me. I mean, would the prequels not be about Anakin’s fall?
They could have been about Obi-wan’s failure as a teacher instead.
Back to terrible ideas: The Neimodians and Trade Federation. Nothing scares me more then something called The Trade Federation. And their ships were unimposing and nonthreatening in design. Compare them to the Star Destroyer. However they did give us the best dialogue in the prequels: https://www.youtube.com/watch?v=gV8QO9dZKVc