One workaround could be:
I assume that you have a constant value of operational cost on each edge in the network. If that is the case, you may try to set the unit of your operational cost as a time unit in the network dataset and use it as the time impedance. Since travel cost on each edge is calculated as travel time (which is operational cost in your case) * CostPerUnitTime + travel distance * CostPerUnitDistance, you will need to set a proper value for CostPerUnitTime, i.e. 1. The solution will show you the low cost order assignment and sequence. However, all the time information output becomes meaningless and you shouldn't use any time windows in the problem setting. You may load the order assignment from VRP solver to Route solver, and choose a true time impedance to obtain the valid time output information.
Hope this works for you.
Thanks.
Anna