Is this an available add-on?  I really need something like this. 

 

We are creating a fairly large and comprehensive series of methods that will allow greater flexibility on how shipping is handled. I would like to evaluate how your example fits into what we are already working on.

In response to those limitations, we have created this:

 

As you can see, this tool allows various shipping methods that are configured to the store to be excluded under certain circumstances.  We are currently in the process of expanding that functionality to incorporate the "flat rate" shipping methods.

 

What you are asking for is yet another set of custom rules which would need to be applied to shipping. It would require a (free shipping) flag as well as a pair of flat rate shipping amount fields added to the product table.  These fields, and a certain amount of logic, would need to be introduced to the shipping choices page.  Logic would have to be created to reflect whatever is needed to deal with how other items are shipped in your store.

 

Let me know if you would like a custom solution created for you.