On "retooling SAP": SAP deliver their systems with all source code and dev platform included, and that may help convince some customers to go for SAP.

However, those that embark on deviating from the well-trodden path are going to be in trouble soon: after every update, potential changes made need to be re-done or edited or at least tested. So as the parent suggests it's really better to adjust the business process if you can.