Is there any easy way to merge multiple XSDs into a single one?

Question

To be more specific, I have a few (quite big) XSDs that are follow some common structure, but generally quite different. I also have to make a single XSD for merged XML files that should combine their respective XSDs.

Example:

<Container>
    <File id="id1_that_use_xsd1" />
    <File id="id2_that_use_xsd2" />
    <File id="id3_that_use_xsd3" />
</Container>

Each existing XSD is used at most for 1 File element, each id attribute is unique and can be used to determine which XSD to use.

Use of a single-file XSD is a requirement.