The short answer is no, PureCloud does not support the ability to build a custom SAML integration. PureCloud is a SAML Service Provider. Our approach follows a client integration strategy as it relates to supporting SAML and OpenID Connect (Q42016 target) Identity Providers (IdP). Rather than take an open-ended approach to broad standards which are open to interpretation, PureCloud will focus on enabling quick, client-side integrations. The strategy limits the exposure of our teams to the burden of support and focuses our developers on iterating through features focused on enabling collaboration, communication and customer engagement. Although customers will be reliant upon our development teams for IdP integrations, we will continue to iterate through them as we move forward. If you do not see the IdP you require, let us know so that we can gauge market need and potentially build the integration.
As of this posting we support OneLogin, Okta, Salesforce, ADFS and Azure AD Premium as integrated Identity Providers. You can stay up to date with the latest list of supported IdPs in the PureCloud Resource Center https://help.mypurecloud.com/articles/about-single-sign-on-sso/