Australia Post Addon Plugin for Marketpress Plugin

I need an ADDON plugin to the Marketpress plugin that will work on both Multisite and Stand Alone Wordpress sites.\r\n\r\nIt needs to:\r\n\r\n* be SEPARATE FROM MARKETPRESS PLUGIN \r\n* I need to be able to upgrade the Marketpress plugin WITHOUT losing any adjustments. So for this reason I need it to be separate from the Marketpress plugin.\r\n* Adds an option on the Store Settings > Shipping page in Select Shipping Method > Aust Post\r\n* Shipping type for each product would be using weight, which would integrate automatically with the Aust Post current postage rates. \r\n* ALL Australia Post Shipping Options in their API functionality must be included\r\n* provide real-time shipping rates from Australia Post using the Postage Assessment Calculator API. like this: [login to view URL]\r\n* shows Australia Post shipping calculations to be included for each product and in the checkout.\r\n\r\nHere\'s the page for Marketpress: [login to view URL]\r\n\r\nThe plugin will need to be installed on my multisite and also my stand alone site so I can make sure they work with the other plugins & themes I use without conflict.