Honestly, after several hundred cumulative days in the various parks, this has never presented itself as a major issue. Certainly not one that would warrant 20 pages of discussion and "strategies". I don't let it get to me, as I have a different approach to the way I look at "lines".
The absolute most efficient way to organize a line is to have one, and only one person per party wait in said line, and then have a gate to allow the rest of the party to join the one person waiting in line at the very front. Much like WDW does with some limited mobility access lines. One person waits in line, and when that person gets to the front, they open a gate and allow the wheelchair or
scooter to move right in. In actuality, it should work this way for all people. If you are going to wait in line at the box office for tickets to a popular concert or a play, do you have all members of your party get in that line, or do you have one person wait in the line and buy tickets for your entire group? Waiting in line for a ride is really no different. If I am the second person in line to buy tickets to see "Lion King" on Broadway, and the person in front of me is going to buy 6 tickets, then I am (virtually) the 7th person in line, irrespective of whether all 6 people crowd the line in front of me or not. Now, if one member of the group waited in line, and at the last moment before that person got to the ticket window, the other 5 members of his group rushed past me to join him, it wouldn't change my place in line whatsoever. I am still 7th in line.
So too at most rides at WDW. I am not going to share a Tea Cup with another family. So if the person in front of me appears to be a solo, but at the last minute, three other family members join him, it doesn't change my place whatsoever. Instead of that apparent solo person riding by himself in a Tea Cup, he now rides with three other people. I still get the next Tea Cup in line. My place in line has not changed, and the outcome of the waiting game has not changed. If I am in line for Jungle Cruise, and it looks like I am going to board
Amazon Annie, (which holds around 40 people), and the parents in front of me are joined at the last minute by their two teenagers, I am still going to get on Amazon Annie. And even if the addition of these two people pushes me back to another boat, then that means that I would have been that last to board Amazon Annie, and I would have gotten the worst center seat. By being pushed back to the next boat, I will be the first to board, and I actually benefit.
In the end, if applied in a logical fashion, queue areas could be made much smaller, and park visits could become much more efficient if the way we approached lines transitioned over to the way we wait in line for tickets. One person per party, while the rest use the restroom, or shop, or rest, or whatever. When your group leader gets to the front of the line, you join them. Now, I know that WDW isn't operating under this system, but since that system is most efficient, I do not mind if people do that. Had all the people been in line ahead of me the entire time, I would be no worse off. And if people are not making me worse off, then why should I complain?
In closing, picture this scenario at Peter Pan. All members of your family get in line, and you are the last ones in that line. When the next family gets behind you, one person in your group says to the group behind you, "Sir; as you can see, we are a party of four and we are all ahead of you. Would you mind if my wife and kids sat on that bench to rest. When we approach the boarding area, my family will rejoin me. And to make this equitable, you can make the same request of the next family that gets behind you." The family behind you agrees. Then, another family gets behind the family behind you, and they make the same request, and it is granted, and so on. If every family did this, then by the time your family got to the boarding area, each and every group would have their place held by one person. The line would not extend out into Fantasyland, and no one would be better off, or worse off than if all members of all families had occupied the queue, and the Peter Pan death march could be avoided. If you are approaching the line to get in the back and want to know how many "ships" are in front of you so that you can judge the wait time, simply count. Each person reoresents, on average 1 (or maybe 1.3 to account for large families) ships. No one could possibly accuse anyone else of "cutting" because everyone will have agreed to this new, efficient and cordial way of waiting in line. It would be great.
Edit to add: But of course, if there are children in the group, and only one adult, they would all have to stick together.