Develop a way for a user to mark a project as completed instead of deactivating it.
A long time ago I was using dotProject software where a project can have one of the following statuses (tags):
We also added 'Ongoing'. Check this one - http://www.linuxlinks.com/portal/content/reviews/Project/Screenshot-dotProject.png
Except of marking it as 'Completed' is anything else you are thinking about - read only mode only for all except a project owner? Or just a label next to project name?