As with Incidents and Problems, why not have the ability to submit a change from a Service Request? There are times a Service Request can lead to a need for change. For example, Accounting has submitted a Service Request asking IT to make a field change on their SAP report. This is not an incident or a problem but a user asking for a modification, or change, to their report.
My Suggestion is to add a RFC (Request For Change) button as an option at the "Fulfillment" level of a Service Request?