The U.S. Army is working to create a common user interface for seven large UAVs it uses, or is developing. This makes is easier for operators to be switched from one UAV to another. That's a big advantage, as it preserves experience and skills operators already have, and saves a lot of retraining time and expense. Seems like a common sense idea, but the suppliers like to create their own interface, as they spend more money and make more profit. However, the army realized that it is the buyer, and has told the UAV manufacturers to get on board, or lose business.
The One System controller is actually three different controllers, using standard controls, procedures and displays for each. This is something commercial software developers have been doing for over two decades. Apple pioneered this approach, compelling software developers to create products that used standard features. This made life a lot easier for users. The One System controller also includes standards on how communications work as well, which makes life a lot easier for those who share information (usually videos). The army effort is expected to catch on with the other services, if only because the common communications spec for One System will have to be used if the other services want to share video with army UAVs.
The largest of the controllers would be used in a fixed site, for allowing an operator and an observer to fly the UAV, examine what it is seeing, and launch any weapons the UAV might be carrying. The second controller is a more compact version of the first one, and allows an operator to function from the back of a vehicle. The third controller is like the current Rover. This is like a laptop computer that allows ground troops to view UAV video and manipulate it.