If we stick to enabling validation by default for any constrained executable, the switch makes sense. If we don't want to make such an addition at this point of time, the problem might be solved in a way specific to the integration implementation (e.g. our PE):

• There could be a specific property in validation.xml examined by the integrator
• An integrator could provide a portable extension which vetoes it's validation interceptor. A user would have to add this PE to the classpath to globally turn off validation