This question is wired to the topic: When to add another answer instead of updating my current one? - but is slightly different. Here is the story:

A few days ago I created an answer that provides a complete working solution to a question. There was posted another answer and was accepted. I liked the idea. The suggested approach looks really light and I've already tested it. It works nicely, but the answer is low quality.

So, I want to write a comprehensive answer, but I can't make a decision about the inner question: Should I edit the low quality answer and allow the lazy author of the accepted answer to get the benefits of my effort, or should I create a separate answer? What should be the principal decision model in cases such as this one?