Using an old RC controller as a base or using the basic Arduino based controller are very useful starting points but when you need to control complex machinery you need a complex RC controller. As an example, if you have an RC excavator you need two dual axis joysticks to control the book and slewing and you need to single axis joysticks or sliding potentiometers to control the tracks. This is not a standard configuration for most RC controllers so it is easier to design a controller with these functions from scratch.