Can an Item be "assembled-to-order" and "Procure-to-order" in a single Inventory org?

We have a requirement where in an item, if available in the warehouse, be shipped from the warehouse (in the Oracle Apps instance A) and if not available but it is in one of the subsidiary warehouse ...procure it from the subsidiary (different oracle apps instance, , and then ship it to the customer (Back-to-Back order cycle).

I realize that an item, in a inventory org(in our example, the org in the Instance A),  can be either 'assemble-to-order' or ‘procure-to-order' but not both. Is there an efficient way to get through this for the requirement mentioned above?

The work-around we planned for now is to have a dummy org (in Instance A) for Back-to-Back order transactions; we are weighing this option - which involves to have item definitions to suit the ATO and PTO in two orgs. (more of a duplicate except for few item attributes)