While my initial response is I don't like it, its worth considering.
I read that onside kicks, since certain rule changes, only succeeds 10% of the time. I would like to know what the success rate is on 4th and 15 plays (whe the D knows you have to gain 15 yards or lose possession. If it is 50% (which it probably isn't) then the rule change is a fundamental change to the game. If the success rate is only 15%, not so much. Also, the proposal is that the play starts on the 25 yard line. Most onsides kicks are recovered closer to midfield so the losing team has more ground to cover in order to score.
I think if the NFL is serious about eliminating kick offs due to the inherent danger, then this rule or something like it will be implemented to provide a losing team the opportunity to regain possession.
I do not agree with the comment above that this rule will make it difficult to compare era's. It is not a play that influences the result of a game that often.
Not surprised that GS 's fingerprints are on this. He has been advocating for eliminating or modifying kick offs since Eric's injury.