In general I just have pants of different lengths for different shoes, but I could see something like that being helpful in a time like pregnancy, when I basically have one nice pair of jeans. I'm having some ppl issues (they are too long for flats) and don't want to spend for another good pair of jeans that I can only wear for two more months!
I agree with the potential problems, though. I dislike the look of non-properly-hemmed jeans. Also, you get wear lines at the fold.