Hi, Andy.
>Being a SAML authenticated web application, Shibboleth is a given. As this will be the production environment (testing will be done on a temporary VM) it's assumed that oxAuth RP should not be installed. Does this sound correct?
Sounds correct to me so far.
>For self-registration, am I better off using the API provided by oxd and hosting the self-reg site on another server, or using the 'User Registration' custom script and modifying what is presented at <site>/identity/register? I'm leaning towards oxd, as I think this may provide greater control in a simpler manner for registering and enforcing certain criteria for doing so, and changing passwords and modifying account details.
Unless you are fond with default registration capabilities Gluu offers out-of-the-box (they are quite basic), the recommended approach at the moment is to create your own app which will handle registration and then will push new users to Gluu either via SCIM or by directly writing to Gluu's (or your corporate) LDAP server.
>If I am to choose the oxd method, I'm a little unclear as to the purpose of oxd-to-http; would this be used if gluu-oxd-server is installed on a different server to the self-reg web pages? Is that even possible?
That's correct, this allows for one oxd server to be available for several apps running on different hosts. A default setup expects that app runs on the same host as oxd server.