Hi,
My two cents here.
Based on what you have answered your best bet is what Ju has indicated. That is the simplest form of business process.
If you have ATP and MRP working this would easily work. It would involve hand shake and hand holding for some length of the process but that you are pretty much doing today too.
You do not have any need of Customer Specific Stock and your is not a Made to Order Scenario.
Thanks.