Whenever I look at a change like this, I try to make sure it wont detrimentally affect other parts of the game (unintended consequences). I always have a number of games on MySky, I try to apply the suggested scenario to one or two of those games and try to imagine what effect it might have. In the case or your scenario, making any player within 10m either side of the LoT as being there to form a lineout, I did this, and here is what I found.
Players who approach the lime of touch cannot leave it until the lineout is over - Law 19.8 (d)
There is an exception that player may leave to match numbers - Law 19.8 (e) and (f)
There is also another exception. One and only one player is allowed to leave the line of touch once he has approached it... the player who does so in order to attempt a QTi
[LAWS]Law 19.7 (g) At a quick throw-in , a player may come to the line of touch and leave without being penalised.[/LAWS]
With a kick to touch, you have members of both the kicking team and the non-kicking team in the area where the kick was taken, and more players from both sides in the vicinity of where the ball went into touch. In short, players from both sides are often all over the field, and the upshot of this is that, if you count everyone in the 20m space centred on the LoT as being there to form a lineout, that could well include some backs from both sides, while some forwards from both sides might be outside that area. Those backs technically cannot leave until the players line up and the throwing team establishes the numbers. The backs also cannot go to their usual positions beyond the 15m line because the LoT ends at the 15m line.
You have also created a difficult job for the referee. Not only will he have to ignore the Law into order to have a normal lineout form, He will have players walking in all directions and he is going to have to try to work out which players are heading for the LoT and which aren't. If a management guideline causes a referee to have to ignore Laws and second guess player intentions, then that is not a good guideline IMO.