I'm using an IBU2 Tank control unit in my excavator. As the name suggest this is meant for tanks but these also have tracks also so you get forward backwards on 1 channel and steering on another channels. Plus two more dc outputs on the other channels for turret turn(excavator skew) gun up/down (i'm not using this but could be used for a boom raise/lower.)
Got basic headlight on/off control (from 4 channel radio) and synchronised sound effects which can be changed on the supplied microSD card.
Obviously it's meant for a Tank so some functions not suitable and needs a bit of tweaking to suit the application.
http://www.ibu-electronics.com/