I think we should revert to college-like rules on PI.
If you think about it, most truly legit PI happens in short to intermediate yardage, where a fixed penalty (and first down) would be enough. On longer throws, PI calls are usually the result of a QB throwing into coverage, or if the receiver is truly open, underthrowing him.
Yeah, there are a few exceptions here and there. But not enough to outweigh the injustice that happens every time a ****ty throw is rewarded with the assumption it would've been completed.