Actually B, I mentioned it a long time ago, but I will repost my example below, it really is a nightmare in the making ...
The big solution to the problems of multi-party bookings that Disney has thrown out there is that you can "link" groups together, and can essentially book FP+s for your whole group.
I don't know about others, but Its not likely I would be willing, or I think others are willing, to let someone else book all their FPs, for themselves and their children, especially if there are differences in children, height, tolerance for rides, etc. If not, then basically we have to send out emails, like ok so May 2, John and Cindy Space mountain, 7DMT, Splash @ MK, Mid day, 5 yr/o Grace can't ride Mine train or Space, so they will FP Dumbo and Peter Pan and splash, 10yr/o Robbie will ride with Frank on SM, 7DMT, but doesn't like to get wet, so they will do Haunted mansion, Grand parents Lynda and John will Do Splash, and 7DMT but don't like SM, so they will get Dumbo, and Melissa and Paul will split their 6yr/o and 9 yr/o ... blah blah blah ....
Ok, now add into that the kids change what they want to do, who they want to do it with, etc etc. Now that's just for planning ONE day, and that was not even the whole day, trying to coordinate with a smallish group, through a single person.
What happens when people want to do it themselves, then you are going to get all those groups getting different times, etc etc. And nothing is going to mesh up.
This just sounds like an absolute nightmare for planning.
Let ALONE that you are supposed to KNOW all this, who (which kids, adults, etc) are going to do which rides, what days, at what TIME, 60 Days out !?!?!?