The problem with your way of thinking is that if Lucas would've gone that route, he would get accussed, as he does now for the Prequels, with have little to no substance in terms of character.
What it essentially comes to down to is that there are two versions of the Prequels that would've essentially worked, your idea which I think reflects the majority of the Star Wars fanbase who aren't too crazy about the Prequels and the version we have now.
And for you, you don't want to sacrifice the Original Trilogy, whereas Lucas wanted to turn the Original Trilogy, especially Vader, on it's head.
Hell, I even questioned why he didn't have Anakin as a teen in Episode I but I saw the thematic devices he used that were the starting point of him sliding to the Darkside and I agreed with every point because it was exactly the opposite I think people were thinking when they wondered what young Darth Vader was like.
Man, that was an amazing run-on sentence.