We use the resubmit for approval process with projects that start as projects to do research, sizing, planning, and then resubmit them for approval once we want them to go through the prioritization and project approval process. The original project that you create stays in the "project world" while it is moving through the approval process again but its not working as well as we would like.
Once you resubmit it for approval, you are no longer able to add/edit reviewers, edit the project profile, etc from the Project Request tab.