Actually, thanks for the insight to both of you. I don't know if the "final level" is the last of the singleplayer or some additional bonus content or what. I know if I got to the very end of sp on Veteran, and then couldn't finish it, I'd be pretty pissed. Probably pissed off enough that I'd not re-play the entire game on a lower difficulty level just so I could finish it.
I like games that allow adjusting difficulty level on the fly, or at least at the beginning of each chapter.