I think that the "not 10m" should be abolished. The team who want territory will kick a long kick. The team who want ball will kick a very short kick (or Rugby League's "Play the Ball").
By this we can abolish the difference of laws between 15/10 and 7. In the Sevens the side who scored does kick-off, because the ball-holding is more important than territory. If we abolish "not 10m", the side conceded points can do kick-off. Then we can abolish the difference of laws between 15/10 and 7.