[gb2world]

I likely don't fully understand your requirement, but I think the BSC backorder mod would do what you describe. You can change the messaging visible to the customer to whatever you want - you don't have to call it back order or pre order, you could have it say "allow xx days for delivery" and set that for the variant combinations that you do not keep in stock. You also do not have to use the words "Out of Stock". In your administration, the order is placed in a backorder queue, which you can then manage in ways that fit your process. I would run the requirement by the people at BCS - I find them to be very helpful with questions and they are willing to make customizations to their products if it is not exactly what you need.