Thank you very much for your response Lars. For the majority of the trial-kit process, the recent versions of Odoo are far superior to other software. It's a shame it doesn't yet go this extra step. My client's legacy system (1990's-era desktop dinosaur) has this additional functionality. 

My client, based in the UK, uses some expensive components that come from China and have long lead times; therefore, they are very careful about the levels of inventory they keep.  The benefit of this "how many can I make" functionality is is that if a customer asked "what's the most you could supply immediately" (immediately being in the minimum possible timeframe to manufacture from materials currently on hand), they would be able to answer. They don't even need to raise MO's for the sub-assemblies before they can see how many finished products they have components for; the system is sophisticated enough to calculate that they have qty x components, which is enough to make qty y sub-assemblies, which is enough to make qty z finished product. This is not the first client that has asked me about this.  It would be great to see Odoo add this at some point.     

Odoo does not support you what you ask. When you have created a production order, status is 'Waiting for components' until all components are available. 

The status do not stop you from starting to produced, of what you have. Confir  it and create a backorder for what is lett.

In the manufacturing order you can see how much you have available / reserved of components. 

There is areport from BOM, that show avsiabilityof components