I think it would be really neat to have a shortcode generator for MarketPress.
**This includes global options as well. Let's not forget the Super Admins
My vision would be a primary choice for what the user is trying to do. Ex "Product Tag cloud; Product List, Global Product List etc..."
Then from there they can choose the optional attributes they want. This should be mixed with radio buttons, drop downs, and user input fields in correspondence with the amount of variation that attribute may have.
At the bottom of the page it would have a shortcode being generated from the options selected above. A user can simply copy and paste and continue designing. Simple!
This would be neat to have in the admin panel of wordpress, especially when you are offering a service on your site to sell things using marketpress. I don't want users to have a difficult time getting exactly what they want, where they want.
If not, a web based simple program would do the trick too.