The only time the combine operator should be responsible for loading the cart is if a) you have a cart driver who doesn't know the job or b) you are topping and have a setup where you can't see in the cart. 

A tall tractor makes seeing in a non-issue if you load the cart from the rear.  Short tractors just have visibility problems.    Our cart has a window in the front but a common mistake is to let the window get covered before it is loaded.   

I think the camera's would be a great idea.   Needs to go on the "to-do" list.