It seems as if we haven't seen or heard of any significant rule changes for a long time. I'll bet some fans on this board have, or can come up with, some good ideas on the subject.
Two areas that I think can be improved are (1) come up with a fairer way to allocate challenges, and (2) the tuck rule -- either explain it and the rationale behind it so that the average fan (like me) can understand it, or drop it.
Two other hazy areas that I think bear scrutiny are (1) should the goal line extend all around the earth? (I believe that is the current interpretation) and (2) is it fair to the receiver that the 'force-out' has been eliminated?