Just as you have added the ability to auto update, and to select new apps, can you add an option to the Manage Menu to uninstall apps.
This form would be much like the add new from, but all the check-boxes would be checked, and unchecking them would uninstall.
Of course the check-box operation could be reversed, only check the ones to be uninstalled.
This would make it easier for me to try out and then remove beta/testing versions. Right now, I have to remove the libreoffice test, which is older than the release version.