Lock Transitions on Project Workflows

Right now we have the ability to lock the transitions for task workflows but not projects.  From a PMO perspective, I would like to lock the transitions on my project workflows in order to force a project into a stage-gate review step at the end of a project to ensure that a proper post-mortem is conducted.

Alternatively if you can't lock the transitions on a project workflow the ability to automatically have an approval initialized  when a project status is set to a certain status would also work.