I'd prefer common sense. It's to be used for "clear and obvious" errors, if the assistant ref didn't flag it and you can't visually see that it is clearly offside, don't change it. No need for lines at all - just makes a mockery of it. The advantage should always go to the attacking side IMHO. We want goals, not disallowed goals
On another point, I'm actually quite impressed with how often they get stuff right on the pitch.