If it's subtle and as emotional as BM needs, it could add a lot of eerieness and pain that wasn't there before. I think there's so many ways a BM band can use operatic vocals. I wouldn't even look at what's been done before. Just think of what else you can do. I'd definitely be interested in hearing it.
I say you give it a try and see how it works and if you and your friends go wit it.
Personally I wouldn’t mind as long they are combined good with the music.
Like everyone else said....it depends on the songwriting and sound.
If you do something, anything, right...it will be good, and break the mold and explore new grounds. Don't dismiss something you like which might have promise, just because people on a message board tell you not to.