Plan Supply based on actual demand, not forecast

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Customer wants to 'plan to order', not to forecast. They want to use actual demand (presumably, sales orders) as their demand schedule in supply planning. 

1. If Demand Management is used (so they can also do comparisons between the system-calculated forecast vs future sales orders), what is the recommended way for Supply Planning to plan based on actual sales?  Would it be as simple as adding Sales Orders measure to End Item Demand measure group so the Supply Plan's demand schedule can point to Sales Order as the demand measure?

2. If Demand Management is not used, what approach is recommended?