The KO return is one of the most exciting plays in football and the on-side kickoff increases late game strategy. I wouldn't want to see either removed. But how would you replace it? A punt? Giving the other team the ball at the 35? The 25? The 20? What if there's a penalty assessed on the kickoff - does it apply to where you spot the ball?
I always thought the PAT was the most pointless (pardon the pun) play in football. Just give them seven points unless they elect to try for two.
I miss the old Mile High Stadium.