Always been intrigued with this idea.
Punts are considered to be safer for players than kickoffs. But, abolishing the kick-offs also abolishes the on-side kick. So, giving the scoring team a 4th and 15 on their own 30 (instead of a kickoff) would allow (1) a punt instead of a traditional kickoff, (2) a replacement for the onside kick by running a play to go for the first down on 4th & 15, and (3) a surprise onside kick with a fake punt.
But, if you fail in going for it, the opposing team might get the ball on your own 30, which is far worse than a failed onside kick, which usually results in the opposing team getting it on the 45 or so. But, I would think a 4th & 15 play might have more success statistically than a non-surprise onside kick?