Fixing invalid HTML

In V3, how should we deal with input HTML like the following?

<span style="color: Red">
  <p>Line 1</p>
  <p>Line 2</p>
</span>

I would like to output:

<p><span style="color: Red">Line 1</span></p>
<p><span style="color: Red">Line 2</span></p>

In other words, the editor will fix the HTML to have a valid output based on the XHTML 1.0 Transitional DTD.

This is something I have worked in the past with Johnny Egeland and that I'm about to bring to life. But, will people out there blame on me because of this?