An insane plan by an insane man...who always thought the ends justified the means even when he was sane.
It's worth specifying that Lelouch's own brand of insanity is very different from Light's though.
Avoiding some of the tragedies would be easy, or so it seems, but unless you change the man...
...you're asking for a change in the universe around him where all the bad luck is replaced with good fortune.
That way we would have a more constructive story but perhaps things would have been more boring as a result.