There's many risks involved here that rather outweigh the apparent benefits;
1/ for better or worse, it is illegal. This matters not a jot to most people who do it because they don't see, or don't believe, the sort of inertia that the justice system is capable of picking up when given the chance. What starts out as an "easily reversible" mod can, in the worst of (but all to common) circumstances turn out to be the worst thing you ever did. For instance, don't assume that your insurance company will cover you just because you've declared it to them (if indeed you have). They're not lawyers, and they're not VOSA inspectors, but they'll take your money knowing their cover only applies if the car is roadworthy. This will bite you. If, in one of many possible hypothetical situations, we were to have a coming together and I crashed into the back of your car (a situation that would ordinarily be completely my fault), my insurer would attempt to turn the tables and claim the damages from you, since you had reduced the effectiveness of your position markers, lights and reflectors to a level below the legal minimum standard. The car is not roadworthy, and thus illegal. Your actions would be deemed to have been a contributory factor, and you can bet your last pound coin I'd pounce on the get of jail free card you'd just handed me, and grab it both hands. "Impossible to see his brake lights" would be my cry, as I fiegned every injury going from whiplash to a paper cut for the insurance company claim form.
2/ Your insurer may well then turn around and tell you that since you have modified your vehicle to make it illegal, then your insurance is null and void. My insurer, having bought me a brand new car, would then sue you, personally, to pay for my new car.
3/ If, heaven forbid, you were to be involved in an incident that was rather more serious and someone were to die or suffer life changing injuries, then you can expect several months of sphincter loosening anxiety attacks whilst the legal beagles work out if they can make a case stick that you might share some element of responsibility. If so, then expect several leather bound judiciary volumes to be hurled in your general direction. I actually know a chap who had this happen to him, and his simple failure to display his rear lights on a dark road rapidly cascaded into a situation that involved much carnage, a broken family, a horrific death, and ended up with him serving time in prison.
4/ the result from that little saga could then result in further hardship, since the civil action from the affected family will take the shirt from your back and the roof from over your head. Goodbye S3, hello Y plate focus estate serving as both your car and your abode. Assuming you'd managed to get your wife/husband/partner to stick with you this long, this would probably be the final nail in the relationship coffin.
5/ even if the above seems far fetched (it isn't), then even in the most harmless of situations you can expect the police to treat you like an idiot, because in their view, only an idiot would tint his lights and windows so they didn't work properly. Taken to the sorts of extremes I regularly see here in East London, this means lots of stop & seaches, lots of tickets, lots of aggro, and if they're feeling particularly irritated, the car will be prohibited from being driven on the road until you've rectified the problem. That means you get to look like a total **** while they humiliate you by making you peel the tints off in front of a crowd of onlookers, or you pay to have the car towed away, or you leave your precious car at the side of the road in whatever town / village / inner city sink estate / industrial park you happen to be in...
6/ ... I saved this one 'til last, as I didn't want it to taint the arguments detailed above. Point 6 is this;
Let's face it, its the sort of boy racer mod normally reserved for 15 year old Hondas sporting stretched tyres and ridiculous camber angles. It really doesn't suit an S3 of such recent vintage, which has rather too much class to be adorned in such a manner. When weighed against the potential for calamity because you've made your car illegal, it's borderline insane.
