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If you can't deploy an SP on the relevant web servers, then you will have to deploy something else in its place. You can combine that something else with SAML by connecting that solution with an SP and constructing a gateway to/from the additional authentication protocol. You are responsible for glueing that together and making it work. The software will neither help nor hinder you.
See also this page describing a description of the general application model that underlies the software to understand better how deployment of the SP works and what it does well and not well.