Hi Jim Acree,
Reviewing through your description:
What is the impact if I deactivate (or even delete) the newly created account and then modify the existing account to reflect the new user login and name?
This will most likely be the steps you need to take in order to update the user's account in both your Jive instance and external identity provider. However, I would recommend submitting a case in your customer group as a next step where a member of our support team can assist in reviewing your specific SAML configuration and providing a more targeted response.