We have implemented a Pack Ship system for multiple carriers- Cargoware. Currently we can ship UPS all services, Fedex, LTL carriers etc through this system. And this is integrated with Baan. We have streamlined the shipping process. for e.g. We don't relieve the inventory until carrier picks up, we move it to a logical warehouse. Also using EDI we get the entire package details and informs customer service of any problem with the packages. So there is lot that can be done once you have the information. We also publish the same information on our B2B site. Our customer can look what is packed in each box and tracking info etc.
In my opinion developing a pack ship system is not a difficult thing. I was working on a similar project- Web based pack ship system to be integrated with Baan.We used Java and XML,but were not able to make it functional as project was put on hold. But if you have resources to do it you can write a XML based intergation with almost all the major carriers both parcel and LTL. You can also integrate this with a export documentation package. There are export system that can be integrated using XML. If you have 3-4 months to do this project, it can be done during this time.
In this way you can get a more robust system, with no license restrictions etc.