Based upon my understanding we can select the operations in routing based upon characteristic values, and you can have operations corresponding to possible value selection and this operations will be selected based upon value selected in sales order. It will be easy approach.
Otherwise If you are looking forward for changing operation time in routing operation you can go through below piece of sap help , you can use referance characteristic and change timing's based upon values selected.
Master Data References in Task Lists - Variant Configuration (LO-VC) - SAP Library
please check and reply , I specially didn't understand when you say scheduling time which field in routing you are talking about , you can check table - field name and include in reply.
Thanks
Ritesh