I would change the one teaching that I believe is the seed for all the other "bad" things that have happend. That the faithful and discrete slave are a channel to God that stands between man and Jesus.
Jesus made it very clear that HE was the way the truth and the life - he did not include any other person or organization, not his apostles, not his future church, NOTHING or NOONE was included in his statement.
I believe that if individuals went directly to Jesus for their guidance as they are commanded to in the New Testament, and not men who try to circumvent his power and authority, then most of the other man-made rules that have caused so much pain would dissolve.