Feature Request: More grid columns controlled by category or by shortcode

In MarketPress, the maximum number of columns in the product grid is 4 and it is sitewide.

I'd like to see three things:

1. The ability to specify more columns - perhaps up to 8.
2. The ability to specify the number of columns for each category separately.
3. The ability to specify the number of columns on the shortcode when displaying a grid.

Please look at the following two URLS. One of them is 3 columns, the other is 4. This was done using CSS and using this method, the maximum is 4 columns. We'd like to 5 or 6 columns:

While on this page, 3 columns is ideal: