That is not too complex, this is something that you can handle with DataAssist.
The idea is that you would need to first have a table in your db to hold the configured items. Along with the columns that you have for the cart this table will also need to have some reference to the user, you can just have a userID column for this.
Once your table has the columns to hold all of the items details and the userID you can add in the insert server behavior. You can have a button for 'save for later' like you have described. You then just insert the DataAssist insert server behavior to get this record into your db. You would just bind the value for the columns of your table with the posted values from the add to cart form just like your add to cart server behavior.
If you have any other requirements or ideas for this let us know and we will be glad to help you get it worked out.
