I don't think the first one is possible but the second may be.. In the SD.IncidentManagement project -> Initial Diagnosis model -> Initial Diagnosis Workflow Dialog component -> Interaction Setup tab -> Reassign Incident. If you edit that model and go to the Conditional Use Model you'll see that there is logic there to not display the link if it's a subtask.
If you make it show the Reassign Incident link then you can probably reassign the subtask to another person/group but I haven't tested it out to see if it does.