TorgosPizza,

This is really off the top of my head stuff, but maybe what you want to do is use the standard product to describe your files and allow the user cart experience to be the same as if the product was shippable. Doing this would make worries about supporting SKU's etc moot. Then in the order_confirmation process you extend the customer confirmation template with a call to a routine that builds links to the files and delivers these links to the customer via the customer purchase confirmation template?

The links could be to a file delivery mechanism that deals with limiting the number of times the link is usable, etc. However the distribution of the file is managed, you are past the sale at that point and it is no longer a cart/inventory issue.

Am I anywhere in your ballpark?

Steve