If you remove the trims this will not trigger the air bags the hiden screw is behind the airbag symbol at the top of the a panel and b trim > Although one recomendation is that the wire should not be run in front of the airbag or simply tucked into the trim as during deployment this can cause harm or failure .If you are still worried dissconect the battery ensuring you have radio code wait 2minutes and touch the negative and postive battery leads together to discharge the systems note this is the two main leads being fully dissconected from the battery and if a second battery is fitted in the rear ie twin battery concept must also be off this ensures no residual voltageis left .A long way around I know and the need to reset 60% of your profiles when complete and some lamps may illuminate after on the dash but a short test drive should go out .One final comment do not reconnect battery till fully rebuilt
In Oz we have brackets for CB antennas that bolt on the front guard and sneak out through the gap between the guard and bonnet. You may be able to get something similar.
If you decide to do that, you can then run the antenna lead out of the cabin through the LHD bonnet release cable hole. If you look in the engine bay you'll see where the bonnet release cable for LHD Touaregs comes out. Knock the bung out and run your cable through there. A bit of silicon sealant and you're away.