We had the current 3def rule for a very long time, but still there are periodic discussions about it.
One clear change would be to play with a custom map, which has a drawn line the 4th player of the defending team is not allowed to cross/or touch at all.
This would make the 3def rule way simpler but also the game somewhat more rigid.
so far the line is drawn here, it could be moved closer to the goals for the strict line.
The line for the possible new map would be more like a soft green to be not distracting.
If the custom map gets a majority, where exactly the line would be if its no crossing or no touching can be decided afterwards.