I should add more detail as I only presented a simplified case initially.
The final assembly can have multiple sub assemblies. When the final assembly is to be produced, any combination of these assemblies could be in stock. Ideally all should be in stock, but we know this is not always the reality.
The requirement is to use sub-assemblies in stock as if it were a single component (line item). The ones not in stock should explode to its constituent components. Availability check then runs on these and the order is then released to floor if components are available.
So it's not a true phantom. It should only behave like a phantom if there is no stock.
Thanks!
Anoop