One difference with daylight and the current rule is that in the daylight model, the attacker is already getting such an advantage that marginal calls going against them probably won't be intuitively seen as overly punitive and bureaucratic. What we are doing now feels so joyless and out of step with the spirit of the game, to me.
Obviously, it isn't all win-win-win. It could effectively destroy the mid-block, resulting in lots of ultra-low block bus-parking.
The question of where the line is drawn has to be addressed, though. It isn't working the way it is now - and I simply do not accept that this is the best we can do.
Another model would be to fix the line to one part of the body that is clad in an already-regulated piece of kit. Compare only players' feet, for instance, because boots are regulated and therefore you don't have any goofiness of being offside by your hairdo. Leaning becomes legal, and it only matters where your foot is relative to the part of the defender's foot closest to their goal.
The problem with this idea is that it probably only works well in technology-supported refereeing environments, and becomes difficult to implement at grassroots.
That's why the daylight rule, flawed as it may be, becomes the natural thing to at least try.
