Conrad; I think you could easily attach an external light bar to the same bumper reinforcement I have used in a small project.
I first attached two Hella lights directly to the bumper hoping there was enough material for it to hang on to. They never fell off, but they were really moving around when I hit uneven road (and we have lots of that around here). The lights were mounted to a steel plate which goes between the bumper and the license plate. The bumper is only 3-4mm of plastic with nothing behind it, so naturally, it will flex with all the added weight.
I originally planned on getting a bull bar even though mounting a new one was outlawed in my country in 2007. I'll probably still get one if I can find a fair-priced used one. Until then, I've had to do some reinforcement of the bumper.
Behind the plastic bumper there is already a reinforcement made of steel, but it sits below the license plate and there's a gap between it and the plastic bumper. I welded a steel plate on top of the reinforcement so that it sticks up behind the license plate. Next, I attached a small wood plank to the new steel plate so that it touches the inside of the plastic bumper. After refitting the bumper, the steel plate holding the lights and the license plate can be reattached and screws will go through the bumper and into the wood. I'm very happy with the result. Here are some pics:
