In my opinion, there are more reasons to ADD the lenses; than there is to not add them. Because the positives outway the negatives.
1.) As much as peopl say it would look stupid, it wouldn't. These guys are professional and know what they are doing, and would make it cool. (or maybe not because they would have gotten the mask right the first time, hehe jokes)
2.) Protection, ya there is his mouth, but that was Bob Kane's doing (the man is a genius). It is how he started Batman's mask. But Batman DID have lenses in the comics, in the cartoons. THIS IS A COMIC BOOK MOVIE PEOPLE
3.) From far distance, his appearance of having no eyes would be horrific. It would make him even more intimidating.
4.) Up close, even scarier. It will scare the crap out of people even more, looking into these blank eyes, where there is nothing, but cold, and darkness.
5.) Obviously the identity factor. It will conceal his identity better. Make him less recognizable as a human being also.
6.) The night vision could be added, which would give him an up on his oponents even more than he already has.
7.) The fact that it would make it even more original than the Burton films.
It all adds up guys. It is more original, more true to the comics, scarier, safe, and helpful. There are so many positives to the lenses if done correctly.

They could work, they would work, they SHOULD WORK!
Lenses... ...Dammnit!
--dk7