you have written, or so i understood, that you want a release strategy for reservation. There is no standard release strategy for reservation. hence you may have to do this thru workflow.
another simpler way for reservation may be by authorizations where goods movement permitted check mark is permitted for only certain users. but in this case it may not be possible to have orignator - approver relationship.
in planning run, when PR is created by MRP, it will follow the release strategy maintained for PR.