The requirement is best implemented with Status Transitions plus a pinned scheduling/optimization status.
Prevent the Cannot Complete status from transitioning to None so the historical appointment is not unscheduled, and pin Cannot Complete for scheduling and optimization so automated services do not move or reassign it.
In scheduling design, it is important to distinguish eligibility from preference. Work Rules filter candidates that do not satisfy hard constraints such as territory, availability, skills, or boolean conditions, while Service Objectives rank the remaining options. Dispatcher Console actions then use that policy logic to place, move, or dispatch appointments in a controlled way.
The alternatives address different parts of the Field Service model. Allowing a transition back to Scheduled would undermine the historical-record requirement, and Auto-Dispatch pinning alone does not address the broader scheduling and optimization behavior described.
This approach keeps the implementation aligned with the standard Field Service data model and avoids unnecessary customization. Study Guide reference: Managing Scheduling and Optimization - Service Appointment lifecycle; Status Transitions; pinned statuses.