The worst part of the game, and this goes for all other tabletop games, is unclear situations. Who gets hit and who gets removed is crystal clear in 8th ed WHFB. This proposed rule will end up being endless amounts of arguments. This is the one thing that is guaranteed to have me stop playing, arguments. Rules should remove points of arguments as much as possible, then they are good rules.
That is why I like pre-measuring, random charge ranges, etc. I dearly hope 40k will continue to be enjoyable (hopefully more so than 5th!). I find WHFB quite enjoyable