Unconstrained to constrained planning for a single org

For years we have run a single unconstrained plan for seven different inventory orgs. All these orgs have assembly operations and some have fabrication operations as well. We have a fairly vertically integrated model. Most orgs source internally to one another depending upon where finished goods to the customer is assembled. One organization (our largest in terms of volume, complexity etc)  is contemplating moving to some sort of constraint based planning. Who knows Enforce Demand Due Dates or Optimization??? This is still all white board conversation. How would this be accomplished? I don't think you can turn constraint based planning