Not sure I fully understand, if you specify that an element can contain mixed content (elements and text) then it can't be restricted to something like an int. For example what simple type would the following be inside myElement?
Code:
<myElement>The quick <b>brown</b> fox</myElement>
or even
Code:
<myElement><b>3</b><i>2</i></myElement>
As an aside mixed content in general is more difficult to process and is usually avoided for data style XML, it's more often found in document style XML.