How to aggregate multisite products?

I've just created my first multisite. The main site has a custom "magazine-style" layout, where I can pick and choose to feature posts from the various subsite blogs by category - I use the wp three broadcast plugin to publish them on the main site.

I now want to offer the subsites the ability to set up a small shop, and need to be able to feature some of their products on my home page, as I'm doing with blog articles and posts.

The problem is that the broadcast plugin method does not work - that option doesn't show up when editing products, so I need to find an alternative method...

So I guess my questions are:

* How can I pick and choose products to feature in my current category-based magazine-style theme?
* If this is not possible, how can I create a grid-based recent products page for the main site featuring products from the subsites?
* If I use the global tags, how can I control the length of the excerpt text as this defaults to 55 words when published on the main site?