On the desktop version of Lightroom CC I (and many other photographers I know) use batch rating and flagging to select a large amount of keepers or reject photos I might later want to delete. This works by selecting multiple images and than pressing the corresponding number (0-5) to star, p to pick, x to reject and u to unflag. As the promise of the iPad was to be a professional working device it would immensely speed up my workflow. I don't think this would require any change in the UI (because most of us use Lightroom with a keyboard), although adding a star bar and flags would make it easy for the touch users as well.
Batch keywording and metadata editing would help with the organization of the photos and one could easily correct a time delay if the camera wasn't set up properly. This would definitely need new buttons in the UI, but I think it's worth it in the long run.