This is an excellent suggestion. My preferred workflow used to involve moving images from one folder to another once they had been transmitted but when you do that you lose the indicator in the contact sheet about whether an image has been successfully delivered (green), is in the process of delivery (amber) or has failed (red). I no longer do that so having a resend queue would allow me to re-think my workflow and possibly go back to how it used to be. Having a delivered tag that remained when moving folders would also be a great idea.