Nested Spans are a pain and if you START out with the code in Post 2, you will have a disaster because that is only safe with a simple (and IMHO unnecessary, except it is a conversion simplifier) span as you show.
process
Code:
<p class="calibre2 none2">blah blah blah</p>
should work the same.

I am going give a try to eschwartz's REGEX