Multistop Shipment accounting backhaul miles during planning

I have scenario where if my multi stop shipment origin is in Texas and i will stop in NJ, CT, MA, NH, ME. Now we do not use depot or any round trip functionality as we buy service from Service Providers for shipments. We would like to encourage OTM to plan this shipment in a way that it goes to farthest stop first and make deliveries downword (for e.g. TX - ME, NH, MA, CT and finally in NJ). The reason for that is if we have final stop in NJ the service provider can easily get back home with less miles (possibly finding Backhaul shipment by themself) so it will get us discount. This is not know up front during shipment planning.

I wanted to bounce off approach that I am thinking if it would work or not? If any of you have came across such scenario wanted to know if I am thinking right or not?

If i modify rate cost for service provider with either of following rate cost basis with weighted cost would it work? Would that produce result that we are expecting?

Shipment Return Trip Distance Traveled
Shipment Round Trip Distance Traveled