A comment I posted on the NFLUK website about this:
I personally don't like the idea. Done well, a kick return shows off the speed of the game and the importance of blocking. A return can shift the momentum of the game, give a poor offensive team the chance to get good field position after giving up a score, or if defended well back a team into a corner. Surprise onside kicks can be game changing, as can fumbles on the return team.
But, if the league really doesn't want liability for the injuries they supposedly cause, then they need to replace it with something that provides the opportunity to make a strategic difference. So how's this for an idea:
Replace kicking off from a tee with a post-safety style free kick/punt. This kick can be recovered by either team, but not advanced by either side. It can be positioned such that a belter of a kick will reach inside the 20 yard line, but a typical effort will put the ball between the 20 and 30. If the kick goes out of bounds, the 40 yard-line penalty still applies. Rules can easily be applied to put certain restrictions on formations, so a team might be able to get the ball back with a 10 yard onside kick, but with the downside of poor field position, or go for a longer kick with a greater hang time, but an increased risk of giving the opposition dangerous field position.
Of course, focusing on finding other, less reactionary and killjoy methods of improving player safety is a far superior idea.