Regarding the OP’s main question, I’ve found the W/kg useful at my “entry level” ability.
It helped me find both the “ZHCC Feel Good Friday [E]” and the “RO4H Rookie Group Ride [E]” events this week, and the ride leaders/sweepers were excellent communicators and teachers.
These were my first group events, and I chose them after lurking the forums and reading about the challenges of events exceeding the listed pace.
Both groups host [D] level events, so I look forward to seeing if their pacing holds true.
One way to electrify the fence would be to have the drop counter roll backwards if a rider pulls past. Maybe the ride creator could select this from a menu when setting up the event, and tell the participants “the fence is live” in the description? I can see some encouragement/enforcement beneficial in the entry-level group rides.
This would encourage fliers to stick with the group (clearly stated in the event description), or simply drop out and find something faster to test themselves against.
The ZHCC group event had the fence drop out at the end, so that became “hammer time”.
Which was fun!