Shipping module - custom with ability to determine carrier based on weight/volum

[Old Mate]

I need a shipping module for VM2 which will choose a carrier based on various criteria:

1. Select my prime carrier on the majority of orders;
2. If an item is very light or small, will choose a postal service taken from the Australian Post website - this carries live data based on postcode, weight and dimensions
3. For heavy items it will only go one carrier.

Issues:

I sell many items from small and light to large (both heavy dead weight and cubic) The current site cannot work out a customer buying a large item with a small one and it gives a false shipping value; typically a cost using the lighter piece. I then loose money on the freight.
Items can go inside each other and the module needs to calculate that.

Shipping data for the main carrier will be in an excel format (xls/csv/txt), but I need fields in the front end of the cart to change surcharges; i.e shipping costs me $10 but I want to add a surcharge. Ideally this would be a field where I enter that value.
The module must be easy to update; think template manager upload where I find the file in a directory, click upload and away it goes.
The postal side of the module must allow for all types of post offered; express and registered are the main methods used.

The main requirement is it must be simple to use and update. I do not want to go into directories to change values or upload data.

I will also want the module supplied as a zip file and I retain rights to it if I ever want to on-sell it.

I have a similar module in VM1 which can be used for reference.