You would have to specify on what yardline on a kickoff a receiving player was allowed to call a fair catch.
Give Kickers enough time and they will figure out how to sky a kickoff. A player can call for a faircatch on a kickoff in the pros as well. For safety reasons.
The above being said the Tech kicker looked to have the perfect "bloop" perfected.
On a fumble I really dont see how you mitigate that except to say as soon as a player fumbles and maybe the ball hits the ground its the opposing team's ball? turnover?
Crossing patterns are extraordinarily dangerous as well. You can get two players, even from the same team, accidentally running into each other.
The removal of the goalpost from the field was definitely a good thing. Seen a few strange collisions on youtube with the giant H.