Enable SAML SSO on secure proxy server

We have an existing requirement as follows.

The trading partners are required to login to myFIlegateway through SSP Http adapter. SSP should be configured to support SSO using 3rd party application. Below is the sequence of events, should happen as per our requirements:
1. A trading partner hits the myFilegateway URL from his/her internet browser.
2. The SSP HTTP Adapter receives the HTTP request in DMZ zone.
3. SSP Http Adapter should redirect the incoming request to 3rd party identity provider application using HTTP along with some Meta Information required by 3rd party identity provider application.
4. The 3rd party identity provider application will receive the HTTP request and present a page to trading partner to fill in credentials like username, password, OTP or secret question or RSA token number etc.
5. The 3rd party identity manager application will authenticate the user based on the credentials entered and respond back to SSP. The response format will be SAML Assertion Message.
6. SSP should parse the SAML Assertion Message and pass the message to SEAS in the format in which SEAS understand.
7. SEAS (with custom java user exit to be build) analyzes the SAML Assertion Message and validates the SAML Assertion Message with expiry time (mentioned in SAML Assertion Message).
8. Once SEAS validates the SAML, then it creates a SESSION Token and returns the SSO token to SSP HTTP Adapter.
9. SSP Outbound Node sends request to myFilegateway.
10. myFilegateway validates the SSO token with SEAS
11. Once validation is completed by myFilegateway, the user lands on myfilegateway home page.
12. Till the session is alive SSP should not redirect user to identity provider.

Issue:
We understand that, currently Secure Proxy works on principle of SESSION_TOKEN. That SSP redirects the incoming request to 3rd Party Application and can consumes the SAML response in form of cookie/ SESSION_TOKEN in http header.
We want to know if there is any way or any user exit options available to support raw HTTP SAML request and response for interaction between SSP and 3rd party Application.
As per our current security policy SSP does not satisfy the requirements and it has not use.