We can able to convert Service To Incident only for unapproved and New Service Request.

But Here we require  option  a technician can change Service to incident at any stage .

 Because in Service request we have predefined approvals and a mail will first goes to reporting manager or department head once they have approved then it come to technician.

 And a technician will be a right person to define it Service request or Incident request based on the request type.

In our setup we want to convert service request to incident at any stage.