Not having rear reflectors is illegal! If you cover them with light tint spray then you must install reflectors. Also if the rear lights are positioned in a place which reflectors won't do there job effectively then reflectors must also be installed elsewhere (e.g FORD FOCUS).
Your insurance will be invalid even if your parked up especially if visibility is poor or at night. When i sprayed the rear lights of my Generation 7 Celica i masked the reverse light and reflector to keep it legal. It actually looked better than others i'd seen with the whole lenses tinted, most people when tinting lenses end up with a matt finish as they don't spray them right which looks crap!
Same goes with front tints darker than legal. I wouldn't want front tints too dark either as you can't see at night. A mate of mine said you just look for headlights, what if someone forgets to switch there lights on, you end up with a smashed up car that insurance refuses to pay for as yes they forgot to switch there lights on but you was driving illegaly, if your luck you might get away with there costs as it could go 50/50, you'd still get 6 or more points on your licence for IN10 and maybe a CD10 as it was careless driving, a large fine and court costs plus high insurance premiums for 5 years. If this happens within your first two years of driving, a test resit will be required (back to provisional)!
Personally i think it's a waste of time and money to even bother risking this, just for the look, i even think lighter tints look classy and don't like dark tints!