SOAP request from Biztalk 2006 without WSDL

Hello gurus:

I have the following case:

I have to create and send a SOAP 1.2 envelope from within Biztalk 2006. The payload is created through a BizTalk mapping between two XML Schemas. A WSDL for the corresponding service is not available. The communication with the soap endpoint is over SSL.
The general functionality is as follows:
Step 1: an incoming XML message is received; the message conforms to the XML Schema a.xsd
Step 2: the message is transformed according to a Biztalk mapping (the thing with functors, with semantics like XSLT); the result conforms to b.xsd an constitutes the payload
Step 3: the payload is included in a SOAP envelope; the envelope contains parameters from within the payload (aka promotion); See attached example
Step 4: the SOAP envelope is sent to a SOAP endpoint
Step 5: synchronously, the sender receives a status response; this too conforms to an XML Schema.
END

I did have some partial success, but I'm not sure I'm doing the right thing. Any help is appreciated.

Here is how the message should look like:

<?xml version="1.0" encoding="UTF-8"?>

<SOAP-ENV:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance&quot;

xmlns:SOAP-ENC="http://www.w3.org/2003/05/soap-encoding&quot;

xmlns:SOAP-ENV="http://www.w3.org/2003/05/soap-envelope&quot;

xmlns:xsd="http://www.w3.org/2001/XMLSchema"&gt;

<SOAP-ENV:Header>

<tceps:endpoints xmlns:tceps="urn:schemas-TCA:/docs/endpoint.tcendpoint" SOAP-ENV:mustUnderstand=ÓtrueÓ>

<tceps:to>

<tceps:address>receiveraddress</tceps:address>

</tceps:to>

<tceps:from>

<tceps:address>senderaddress</tceps:address>

</tceps:from>

</tceps:endpoints>

<tcprop:properties xmlns:tcprop="urn:schemas-TCA:/docs/property.tcproperty" SOAP-ENV:mustUnderstand=ÓtrueÓ>

<tcprop:identity>(GUID)</tcprop:identity>

<tcprop:sentAt>(PROMOTED DateTime)</tcprop:sentAt>

<tcprop:expiresAt>(sentAt + 10 hours)</tcprop:expiresAt>

<tcprop:topic>Order</tcprop:topic>

</tcprop:properties>

<tcproc:process xmlns:tcproc="urn:schemas-TCA:/docs/process.tcprocess" SOAP-ENV:mustUnderstand=ÓtrueÓ>

<tcproc:correlationid>(GUID)</tcproc:correlationid>

<tcproc:relatedDocid>(PROMOTED int)</tcproc:relatedDocid>

</tcproc:process>

</SOAP-ENV:Header>

<SOAP-ENV:Body>

<Payload xmlns="Declare conformance with b.xsd">

<Content> … </Content>

<Payload/>

</SOAP-ENV:Body>

</SOAP-ENV:Envelope>