OFBIZ-5852 enables you to add a Party to a Routing Task (the WorkEffortPartyAssignment entity), to specify a person who is preferred to perform the task.
If the person is on leave or unavailable, the production manager would have to manually specify a different person.
It would be better to specify skill or skills required for the Routing Task. Then on each production run, any Party with the right skills could be scheduled to perform the task.
There are already entities WorkEffortSkillStandard, PartySkill and SkillType which could be used to enable this.