The tow truck already has the extra power of lowering and raising the boom, so adding in rotation, extension and things like that isn't that hard. The tiller trailer replaces the gasoline tanker, and in doing this you would come upon two problems. First off is that the tanker doesn't have extra abilities, so that would be a hindrance. Second and most important is that when you drive the tiller, you're only driving the cab part. Controlling the trailer is not possible for the first and foremost reason that the game wouldn't know how to differentiate between the trailer you're pulling and some other car passing by. So no, this mod would not be possible.