Unmarshalling xsd with selective element replacement from another xsd - xsd

Question

I am new to working with xsd and jaxb, so if my questions are ignorant, please educate me. Also, if you need any more info, let me know and I will provide what I can.
At our company we are working with xsd sources from a 3rd party. We need to implement a SOAP - Java translation and we have a bunch of .wsdl and .xsd files to work with. We are running into problems with two of the .xsd files. The 3rd party provides a "datatypes.xsd", with a org.hl7.v3 namespace and a "datatypes-extensions-hl7nl.xsd", with a nl.hl7.v3 namespace.
When I unmarshall the xds sources, the resultant .java files get created under a different package, named after their own namespaces: org/hl7/v3 and nl/hl7/v3.
Whereas the 3rd party has intended that, where applicable, the types from "datatypes-extensions.xsd" have precedence and should be generated instead of those in "datatypes.xsd", and in the same package.
What I have tried so far
Since I cannot alter the xsd sources, I have (unsuccessfully) tried 2 things using a .jxb file.
1: generating the .java files in a single directory. This led to overwriting issues.
2: providing a binding to point to the correct type:
<jaxb:bindings schemaLocation="../coreschemas/datatypes.xsd">
<jaxb:bindings node="//xs:complexType[#name='TEL']">
<jaxb:class ref="nl.hl7.v3.TEL"/>
</jaxb:bindings>
</jaxb:bindings>
This worked initially, until I changed the reference of a supertype, at which point the compiler complained it could no longer locate the proper supertype for the extending types.
Sources
The sources are opensource so if you'd like to see them for yourself: https://decor.nictiz.nl/pub/vzvz/kz-vzvz-xml-20190122T131422.zip
The .wsdl:
<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns="http://schemas.xmlsoap.org/wsdl/"
xmlns:hl7="urn:hl7-org:v3"
targetNamespace="urn:hl7-org:v3"
name="OpvragenOverdrachtconcerns">
<documentation> WSDL implementatie van OpvragenOverdrachtconcerns</documentation>
<types>
<xsd:schema targetNamespace="urn:hl7-org:v3" elementFormDefault="qualified">
<xsd:include schemaLocation="../schemas_codeGen/REPC_IN990110NL.xsd"/>
</xsd:schema>
<xsd:schema targetNamespace="urn:hl7-org:v3" elementFormDefault="qualified">
<xsd:include schemaLocation="../schemas_codeGen/REPC_IN990111NL.xsd"/>
</xsd:schema>
</types>
<message name="REPC_IN990110NL">
<part name="body" element="hl7:REPC_IN990110NL"/>
</message>
<message name="REPC_IN990111NL">
<part name="body" element="hl7:REPC_IN990111NL"/>
</message>
The header of response message type: REPC_IN990111NL:
<?xml version="1.0" encoding="UTF-8"?>
<!-- REPC_IN990111NL - Opleveren overdrachtconcerns --><!--Note: this file was generated. DO NOT EDIT HERE.--><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="urn:hl7-org:v3"
targetNamespace="urn:hl7-org:v3"
elementFormDefault="qualified">
The header and definition of a conflicting type in datatypes.xsd:
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:hl7="urn:hl7-org:v3" xmlns:hl7nl="urn:hl7-nl:v3"
xmlns:sch="http://www.ascc.net/xml/schematron" elementFormDefault="qualified" targetNamespace="urn:hl7-org:v3" xmlns="urn:hl7-org:v3">
<xsd:include schemaLocation="voc.xsd"/>
<xsd:import namespace="urn:hl7-nl:v3" schemaLocation="datatypes-extensions-hl7nl.xsd"/>
<xsd:complexType name="TEL">
<xsd:complexContent>
<xsd:extension base="URL">
<xsd:sequence>
<xsd:element name="useablePeriod" type="IVL_TS" minOccurs="0"
maxOccurs="unbounded">
<!-- FIXME: one would expect the name "GTS" here but it's not
SXCM does ALL the right things, it's just not the right NAME. -->
</xsd:element>
<xsd:element name="id" type="II" minOccurs="0"/>
</xsd:sequence>
<xsd:attribute name="use" type="set_cs_TelecommunicationAddressUse" use="optional">
</xsd:attribute>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
The header and type in datatypes-extension-hl7nl.xsd
<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" xmlns:hl7="urn:hl7-org:v3" xmlns="urn:hl7-nl:v3" xmlns:sch="http://purl.oclc.org/dsdl/schematron" targetNamespace="urn:hl7-nl:v3">
<xsd:import schemaLocation="datatypes.xsd" namespace="urn:hl7-org:v3"/>
<xsd:complexType name="TEL">
<xsd:complexContent>
<xsd:extension base="ANY">
<xsd:sequence>
<xsd:element name="useablePeriod" type="QSET_TS" minOccurs="0"/>
</xsd:sequence>
<xsd:attribute name="value" type="xsd:anyURI" use="optional"/>
<xsd:attribute name="use" type="set_TelecommunicationAddressUse" use="optional"/>
<xsd:attribute name="capabilities" type="set_TelecommunicationCapability" use="optional"/>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
Expected and actual results
As stated above, instead of generating two packages according to the different namespaces, one should be created with the "nl.hl7.v3" types being generated intead of the "org.hl7.v3" ones with the same name.
Thank you for your time in advance.
Max