This takes a bit of work but it can be custom coded for shipping for USPS and UPS to know what vendor is doing the shipping ...
However, to complicate it, you need to also take into account mixed orders where one product is from New York and the other from Utah ... this makes it where you need a shipping calculator or charges total per product to build the whole shipping cost ...
I have written things along this line for fixed product shipping which is a lot easier than separate calculations per product on a mixed order ...
While neither exists at this time, it could be done ... I know that I have this on the list of fun things to do someday ... :smile: