Hi, i have read your project description, i understand what you want, and i would like to offer you my services. I can create Magento module that will implement the required features (multiple vendors and multiple origins of shipping), and make them works properly with the rest of the Magento (shipping, order admin screens). I have excellent knowledge of Magento and related technologies, plenty of experience with them, most importantly including experience with creating complex Magento extensions, so i can finish this project quickly and to your full satisfaction. Feel free to contact me by private message if you would like to discuss the details. I'm looking forward to our cooperation.