Hello,
I am an engineer and I can help you : I am used to this kind f optimization problem. If you want, I can even build you prototype before you hire me. If you are satisfied, you buy the solution, if not you can still hire someone else.
From what I understand, I propose to build a single class called PackingOptimization with a methode called "optimize". This function would take three arguments : the path of the input xml, the path of the output xml, and an array for data parameters.
To better help you, I would need the documentation available about the requirements and the format of XML feeds. The price for the project should be around $320 and the time 2days, but it could vary a bit depending on the complexity of your requirements.
I hope we can work together. Please send me a message if you are interested.
Best regards