Hi Keith
It seems that you have two cases:
1) Same WBS element assignment to all of the work order operations - This can be done by using a user exit which will replace the default settlement receiver with WBS elements. (I am assuming that these work orders could be settled to other types of cost receivers, like Cost Centers unless they are assigned to WBS elements.) So if the work order is assigned to a WBS element, then all of the operation settlement receivers will be updated by this user exit. Users can always overwrite them.
2) Different WBS element assignment to different work order assignments - For this one, you may need to develop "mass update" functionality for operations and by using a similar logic to PM/PS reference elements, you may probably use an automatic assignment functionality by using custom fields in operations and NW Activities/WBS elements. .
Regards
Savas