xsd-merge.xslt

<?xml version="1.0"?>
<xsl:stylesheet version="2.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema">

    <xsl:output version="1.0" encoding="utf-8" indent="yes" name="xml" />

    <xsl:template match="/">
        <xsl:apply-templates />
    </xsl:template>

    <xsl:template match="xsd:schema">
        <xsl:copy-of select="document(xsd:import/@schemaLocation)" />
    </xsl:template>

    <xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()" />
        </xsl:copy>
    </xsl:template>

</xsl:stylesheet>

xsd-no-schemalocaton.xslt

<?xml version="1.0"?>
<xsl:stylesheet version="2.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema">

    <xsl:output version="1.0" encoding="utf-8" indent="yes" name="xml" />

    <xsl:template match="/">
        <xsl:apply-templates />
    </xsl:template>

    <xsl:template match="xsd:import/@schemaLocation" />

    <xsl:template match="xsd:import">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()|processing-instruction()|comment()" />
        </xsl:copy>
    </xsl:template>

    <xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()|processing-instruction()|comment()" />
        </xsl:copy>
    </xsl:template>

</xsl:stylesheet>

xsd-nsprefix.xslt

<?xml version="1.0"?>
<xsl:stylesheet version="2.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema">

    <xsl:output version="1.0" encoding="utf-8" indent="yes" name="xml" />

    <xsl:template match="/">
        <xsl:apply-templates />
    </xsl:template>

    <xsl:template match="*[namespace-uri()='http://www.w3.org/2001/XMLSchema']">
        <xsl:element name="xsd:{local-name()}" namespace="http://www.w3.org/2001/XMLSchema">
            <xsl:apply-templates select="@*|node()"/>
        </xsl:element>
    </xsl:template>

    <xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()" />
        </xsl:copy>
    </xsl:template>

</xsl:stylesheet>

xsd-split.xslt

<?xml version="1.0"?>
<xsl:stylesheet version="2.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema">

    <xsl:output version="1.0" encoding="utf-8" indent="yes" name="xml" />

    <xsl:template match="/">
        <xsl:apply-templates />
    </xsl:template>

    <xsl:template match="xsd:schema">
        <xsl:variable name="filename" select="concat(replace(replace(@targetNamespace, '^https?://', ''), '[^a-zA-Z0-9_.+-]', '_'), '.xsd')" />
        <xsl:result-document href="{$filename}" format="xml">
            <xsl:copy-of select="." />
        </xsl:result-document>
        <xsl:element name="xsd:schema" namespace="http://www.w3.org/2001/XMLSchema">
            <xsl:element name="xsd:import">
                <xsl:attribute name="namespace">
                    <xsl:value-of select="@targetNamespace" />
                </xsl:attribute>
                <xsl:attribute name="schemaLocation">
                    <xsl:value-of select="$filename" />
                </xsl:attribute>
            </xsl:element>
        </xsl:element>
    </xsl:template>

    <xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()" />
        </xsl:copy>
    </xsl:template>

</xsl:stylesheet>