To be honest we'd have to come up with a cargo loadfactor algorithm which would be difficult enough. The way cargo works is more about individual one-way flows between certain destinations that airlines optimise by doing multiple stops on each end-to-end journey. The hub and spoke type model is more effectively used by integrators like UPS, DHL, FedEx either for bulk or parcels.
Time could be better spent improving the passenger loadfactor algorithm which is a priority, but it would add some extra depth by adding in cargo. Its just a matter of resources which are quite limited as you may have noticed.