I would go with Matt’s(@MattUribe) workflow idea here. Keep Role B requestable only, with no assignment criteria, & use a workflow to remove Role B after Role C is successfully provisioned.
For the workflow, use `Provisioning Completed` as the trigger. Add a simple filter for the source/result if possible, then use a Compare step to confirm Role C was added before removing Role B.
The flow would be: Role C provisioned → workflow confirms the Role C entitlement was added → workflow removes Role B. The revoke should work as long as Role B was request-granted.