2 Questions About Marketpress and Multi Site

I installed marketpress and everything is working perfectly, love the plugin.

However there are a couple things I would like to do that I'm not sure if can be done without custom coding:

- Custom Shipping: I want people that offer their products to be able to put what they want to charge for shipping (similar to etsy) and to where.

- Global shopping cart: The problem I'm having is that when visitors add a product to their shopping cart, when they return to the main page to look for more items to buy, or if they go to another shop, they lose what their shopping car. (it shows blank and if I add something it only shows that item)

Thanks a lot,
Esteban