Do you have both a low beam light and a high beam light?
If so from what I understand with split systems like that (with no dual filament bulb) the low beam has to be on all the time. Its not legal to switch between them. Hence the low beam would be permanently on via direct link or through a relay. Therefore you only need a switch for high beam. If you going to run extra LED lights or equivalent they can run on a extra switch on your tower that can only function with the high beam on. That way if you kill the high beam so do the extra lights. When the high beam is on I figure you'd want all the lights on, not just the high beam alone.
If you run the low beam via a relay then if you are running only at night in the bush where legalities of your lighting system is not as relevant you can just swap the plug onto the low beam circuit taking away the power draw.
Can you fit one of these;
Stocked through mcsonline.com.au, if your after one let me know.